/text/src/test/resources/examples/php/pleac.in.php

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# -*- php -*-
# The examples are taken from the Perl Cookbook
# By Tom Christiansen & Nathan Torkington
# see http://www.oreilly.com/catalog/cookbook for more

# @@PLEAC@@_NAME
# @@SKIP@@ PHP

# @@PLEAC@@_WEB
# @@SKIP@@ http://php.net/

# @@PLEAC@@_1.0
#-----------------------------
$string = '\n';                     # two characters, \ and an n
$string = 'Jon \'Maddog\' Orwant';  # literal single quotes
$string = 'Jon "Maddog" Orwant';    # literal double quotes
#-----------------------------
$string = "\n";                     # a "newline" character
$string = "Jon \"Maddog\" Orwant";  # literal double quotes
$string = "Jon 'Maddog' Orwant";    # literal single quotes
#-----------------------------
$a = 
"This is a multiline
here document";

$a = <<<EOF
This is a multiline here document
terminated by EOF on a line by itself
EOF;
#-----------------------------

# @@PLEAC@@_1.1
#-----------------------------
$value = substr($string, $offset, $count);
$value = substr($string, $offset);

$string = substr_replace($string, $newstring, $offset, $count);
$string = substr_replace($string, $newtail, $offset);
#-----------------------------
# get a 5-byte string, skip 3, then grab 2 8-byte strings, then the rest
list($leading, $s1, $s2, $trailing) =
    array_values(unpack("A5a/x3/A8b/A8c/A*d", $data);

# split at five byte boundaries
preg_match_all ("/.{5}/", $data, $f, PREG_PATTERN_ORDER);
$fivers = $f[0];

# chop string into individual characters
$chars  = $string;
#-----------------------------
$string = "This is what you have";
#         +012345678901234567890  Indexing forwards  (left to right)
#          109876543210987654321- Indexing backwards (right to left)
#           note that 0 means 10 or 20, etc. above

$first  = substr($string, 0, 1);  # "T"
$start  = substr($string, 5, 2);  # "is"
$rest   = substr($string, 13);    # "you have"
$last   = substr($string, -1);    # "e"
$end    = substr($string, -4);    # "have"
$piece  = substr($string, -8, 3); # "you"
#-----------------------------
$string = "This is what you have";
print $string;
#This is what you have

$string = substr_replace($string, "wasn't", 5, 2);  # change "is" to "wasn't"
#This wasn't what you have

$string = substr_replace($string, "ondrous", -12);  # "This wasn't wondrous"
#This wasn't wondrous

$string = substr_replace($string, "", 0, 1);        # delete first character
#his wasn't wondrous

$string = substr_replace($string, "", -10);         # delete last 10 characters
#his wasn'
#-----------------------------
if (preg_match("/pattern/", substr($string, -10)) {
    print "Pattern matches in last 10 characters\n";
}

# substitute "at" for "is", restricted to first five characters
$string=(substr_replace(preg_replace("/is/", "at", substr($string,0,5)),0,5);
#-----------------------------
# exchange the first and last letters in a string
$a = "make a hat";
list($a[0], $a[strlen($a)-1]) = Array(substr($a,-1), substr($a,0,1));
print $a;

#-----------------------------
# extract column with unpack
$a = "To be or not to be";
$b = unpack("x6/A6a", $a);  # skip 6, grab 6
print $b['a'];


$b = unpack("x6/A2b/X5/A2c", $a); # forward 6, grab 2; backward 5, grab 2
print $b['b']."\n".$b['c']."\n";

#-----------------------------
function cut2fmt() {
    $positions = func_get_args();
    $template  = '';
    $lastpos   = 1;
    foreach($positions as $place) {
        $template .= "A" . ($place - $lastpos) . " ";
        $lastpos   = $place;
    }
    $template .= "A*";
    return $template;
}

$fmt = cut2fmt(8, 14, 20, 26, 30);
print "$fmt\n";
#A7 A6 A6 A6 A4 A*
#-----------------------------

# @@PLEAC@@_1.2
#-----------------------------
# use $b if $b is true, else $c
$a = $b?$b:$c;

# set $x to $y unless $x is already true
$x || $x=$y;
#-----------------------------
# use $b if $b is defined, else $c
$a = defined($b) ? $b : $c;
#-----------------------------
$foo = $bar || $foo = "DEFAULT VALUE";
#-----------------------------
$dir = array_shift($_SERVER['argv']) || $dir = "/tmp";
#-----------------------------
$dir = $_SERVER['argv'][0] || $dir = "/tmp";
#-----------------------------
$dir = defined($_SERVER['argv'][0]) ? array_shift($_SERVER['argv']) : "/tmp";
#-----------------------------
$dir = count($_SERVER['argv']) ? $_SERVER['argv'][0] : "/tmp";
#-----------------------------
$count[$shell?$shell:"/bin/sh"]++;
#-----------------------------
# find the user name on Unix systems
$user = $_ENV['USER']
     || $user = $_ENV['LOGNAME']
     || $user = posix_getlogin()
     || $user = posix_getpwuid(posix_getuid())[0]
     || $user = "Unknown uid number $<";
#-----------------------------
$starting_point || $starting_point = "Greenwich";
#-----------------------------
count($a) || $a = $b;          # copy only if empty
$a = count($b) ? $b : $c;          # assign @b if nonempty, else @c
#-----------------------------

# @@PLEAC@@_1.3
#-----------------------------
list($VAR1, $VAR2) = array($VAR2, $VAR1);
#-----------------------------
$temp    = $a;
$a       = $b;
$b       = $temp;
#-----------------------------
$a       = "alpha";
$b       = "omega";
list($a, $b) = array($b, $a);        # the first shall be last -- and versa vice
#-----------------------------
list($alpha, $beta, $production) = Array("January","March","August");
# move beta       to alpha,
# move production to beta,
# move alpha      to production
list($alpha, $beta, $production) = array($beta, $production, $alpha);
#-----------------------------

# @@PLEAC@@_1.4
#-----------------------------
$num  = ord($char);
$char = chr($num);
#-----------------------------
$char = sprintf("%c", $num);                # slower than chr($num)
printf("Number %d is character %c\n", $num, $num);
#-----------------------------
$ASCII = unpack("C*", $string);
eval('$STRING = pack("C*", '.implode(',',$ASCII).');');
#-----------------------------
$ascii_value = ord("e");    # now 101
$character   = chr(101);    # now "e"
#-----------------------------
printf("Number %d is character %c\n", 101, 101);
#-----------------------------
$ascii_character_numbers = unpack("C*", "sample");
print explode(" ",$ascii_character_numbers)."\n";

eval('$word = pack("C*", '.implode(',',$ascii_character_numbers).');');
$word = pack("C*", 115, 97, 109, 112, 108, 101);   # same
print "$word\n";
#-----------------------------
$hal = "HAL";
$ascii = unpack("C*", $hal);
foreach ($ascii as $val) {
    $val++;                 # add one to each ASCII value
}
eval('$ibm = pack("C*", '.implode(',',$ascii).');');
print "$ibm\n";             # prints "IBM"
#-----------------------------

# @@PLEAC@@_1.5
#-----------------------------
// using perl regexp
$array = preg_split('//', $string ,-1, PREG_SPLIT_NO_EMPTY);
// using PHP function: $array = str_split($string);

// Cannot use unpack with a format of 'U*' in PHP.
#-----------------------------
for ($offset = 0; preg_match('/(.)/', $string, $matches, 0, $offset) > 0; $offset++) {
    // $matches[1] has charcter, ord($matches[1]) its number
}
#-----------------------------
$seen = array();
$string = "an apple a day";
foreach (str_split($string) as $char) {
    $seen[$char] = 1;
}
$keys = array_keys($seen);
sort($keys);
print "unique chars are: " . implode('', $keys)) . "\n";
unique chars are:  adelnpy
#-----------------------------
$seen = array();
$string = "an apple a day";
for ($offset = 0; preg_match('/(.)/', $string, $matches, 0, $offset) > 0; $offset++) {
    $seen[$matches[1]] = 1;
}
$keys = array_keys($seen);
sort($keys);
print "unique chars are: " . implode('', $keys) . "\n";
unique chars are:  adelnpy
#-----------------------------
$sum = 0;
foreach (unpack("C*", $string) as $byteval) {
    $sum += $byteval;
}
print "sum is $sum\n";
// prints "1248" if $string was "an apple a day"
#-----------------------------
$sum = array_sum(unpack("C*", $string));
#-----------------------------

// sum - compute 16-bit checksum of all input files
$handle = @fopen($argv[1], 'r');
$checksum = 0;
while (!feof($handle)) {
    $checksum += (array_sum(unpack("C*", fgets($handle))));
}
$checksum %= pow(2,16) - 1;
print "$checksum\n";

# @@INCLUDE@@ include/php/slowcat.php
#-----------------------------

# @@PLEAC@@_1.6
#-----------------------------
$revchars = strrev($string);
#-----------------------------
$revwords = implode(" ", array_reverse(explode(" ", $string)));
#-----------------------------
// reverse word order
$string = 'Yoda said, "can you see this?"';
$allwords    = explode(" ", $string);
$revwords    = implode(" ", array_reverse($allwords));
print $revwords . "\n";
this?" see you "can said, Yoda
#-----------------------------
$revwords = implode(" ", array_reverse(explode(" ", $string)));
#-----------------------------
$revwords = implode(" ", array_reverse(preg_split("/(\s+)/", $string)));
#-----------------------------
$word = "reviver";
$is_palindrome = ($word === strrev($word));
#-----------------------------
// quite a one-liner since "php" does not have a -n switch
% php -r 'while (!feof(STDIN)) { $word = rtrim(fgets(STDIN)); if ($word == strrev($word) && strlen($word) > 5) print $word; }' < /usr/dict/words
#-----------------------------

# @@PLEAC@@_1.8
#-----------------------------
$text = preg_replace('/\$(\w+)/e', '$$1', $text);
#-----------------------------
list($rows, $cols) = Array(24, 80);
$text = 'I am $rows high and $cols long';
$text = preg_replace('/\$(\w+)/e', '$$1', $text);
print $text;

#-----------------------------
$text = "I am 17 years old";
$text = preg_replace('/(\d+)/e', '2*$1', $text);
#-----------------------------
# expand variables in $text, but put an error message in
# if the variable isn't defined
$text = preg_replace('/\$(\w+)/e','isset($$1)?$$1:\'[NO VARIABLE: $$1]\'', $text);
#-----------------------------

// As PHP arrays are used as hashes too, separation of section 4
// and section 5 makes little sense.

# @@PLEAC@@_1.9
#-----------------------------
$big = strtoupper($little);
$little = strtolower($big);
// PHP does not have the\L and\U string escapes.
#-----------------------------
$big = ucfirst($little);
$little = strtolower(substr($big, 0, 1)) . substr($big, 1);
#-----------------------------
$beast   = "dromedary";
// capitalize various parts of $beast
$capit   = ucfirst($beast); // Dromedar
// PHP does not have the\L and\U string escapes.
$capall  = strtoupper($beast); // DROMEDAR
// PHP does not have the\L and\U string escapes.
$caprest = strtolower(substr($beast, 0, 1)) . substr(strtoupper($beast), 1); // dROMEDAR
// PHP does not have the\L and\U string escapes.
#-----------------------------
// titlecase each word's first character, lowercase the rest
$text = "thIS is a loNG liNE";
$text = ucwords(strtolower($text));
print $text;
This Is A Long Line
#-----------------------------
if (strtoupper($a) == strtoupper($b)) { // or strcasecmp($a, $b) == 0
    print "a and b are the same\n";
}
#-----------------------------
# @@INCLUDE@@ include/php/randcap.php

// % php randcap.php < genesis | head -9
#-----------------------------

# @@PLEAC@@_1.10
#-----------------------------
echo $var1 . func() . $var2; // scalar only
#-----------------------------
// PHP can only handle variable expression without operators
$answer = "STRING ${[ VAR EXPR ]} MORE STRING";
#-----------------------------
$phrase = "I have " . ($n + 1) . " guanacos.";
// PHP cannot handle the complex exression: ${\($n + 1)}
#-----------------------------
// Rest of Discussion is not applicable to PHP
#-----------------------------
// Interpolating functions not available in PHP
#-----------------------------

# @@PLEAC@@_1.11
# @@INCOMPLETE@@
# @@INCOMPLETE@@

# @@PLEAC@@_1.12
#-----------------------------
$output = wordwrap($str, $width, $break, $cut);
#-----------------------------
# @@INCLUDE@@ include/php/wrapdemo.php
#-----------------------------
// merge multiple lines into one, then wrap one long line
print wordwrap(str_replace("\n", " ", file_get_contents('php://stdin')));
#-----------------------------
while(!feof(STDIN)) {
    print wordwrap(str_replace("\n", " ", stream_get_line(STDIN, 0, "\n\n")));
    print "\n\n";
}
#-----------------------------

# @@PLEAC@@_1.13
#-----------------------------
//backslash
$var = preg_replace('/([CHARLIST])/', '\\\$1', $var);
// double
$var = preg_replace('/([CHARLIST])/', '$1$1', $var);
#-----------------------------
$var = preg_replace('/%/', '%%', $var);
#-----------------------------
$string = 'Mom said, "Don\'t do that."';
$string = preg_replace('/([\'"])/', '\\\$1', $string);
// in PHP you can also use the addslashes() function
#-----------------------------
$string = 'Mom said, "Don\'t do that."';
$string = preg_replace('/([\'"])/', '$1$1', $string);
#-----------------------------
$string = preg_replace('/([^A-Z])/', '\\\$1', $string);
#-----------------------------
// PHP does not have the \Q and \E string metacharacters
$string = "this is\\ a\\ test\\!";
// PHP's quotemeta() function is not the same as perl's quotemeta() function
$string = preg_replace('/(\W)/', '\\\$1', 'is a test!');
#-----------------------------

# @@PLEAC@@_1.14
#-----------------------------
$string = trim($string);
#-----------------------------
// print what's typed, but surrounded by > < symbols
while (!feof(STDIN)) {
    print ">" . substr(fgets(STDIN), 0, -1) . "<\n";
}
#-----------------------------
$string = preg_replace('/\s+/', ' ', $string); // finally, collapse middle
#-----------------------------
$string = trim($string);
$string = preg_replace('/\s+/', ' ', $string);
#-----------------------------
// 1. trim leading and trailing white space
// 2. collapse internal whitespace to single space each
function sub_trim($string) {
    $string = trim($string);
    $string = preg_replace('/\s+/', ' ', $string);
    return $string;
}
#-----------------------------

# @@PLEAC@@_1.15
# @@INCOMPLETE@@
# @@INCOMPLETE@@

# @@PLEAC@@_1.16
#-----------------------------
$code = soundex($string);
#-----------------------------
$phoned_words = metaphone("Schwern");
#-----------------------------
// substitution function for getpwent():
// returns an array of user entries,
// each entry contains the username and the full name
function getpwent() {
    $pwents = array();
    $handle = fopen("passwd", "r");
    while (!feof($handle)) {
        $line = fgets($handle);
        if (preg_match("/^#/", $line)) continue;
        $cols = explode(":", $line);
        $pwents[$cols[0]] = $cols[4];
    }
    return $pwents;
}

print "Lookup user: ";
$user = rtrim(fgets(STDIN));
if (empty($user)) exit;
$name_code = soundex($user);
$pwents = getpwent();
foreach($pwents as $username => $fullname) {
    preg_match("/(\w+)[^,]*\b(\w+)/", $fullname, $matches);
    list(, $firstname, $lastname) = $matches;
  
    if ($name_code == soundex($username) ||
        $name_code == soundex($lastname) ||
        $name_code == soundex($firstname))
    {
        printf("%s: %s %s\n", $username, $firstname, $lastname);
    }
}
#-----------------------------

# @@PLEAC@@_1.17
#-----------------------------
# @@INCLUDE@@ include/php/fixstyle.php
#-----------------------------
# @@INCLUDE@@ include/php/fixstyle2.php
#-----------------------------
// very fast, but whitespace collapse
while (!feof($input)) {
  $i = 0;
  preg_match("/^(\s*)(.*)/", fgets($input), $matches); // emit leading whitespace
  fwrite($output, $matches[1]);
  foreach (preg_split("/(\s+)/", $matches[2]) as $token) { // preserve trailing whitespace
    fwrite($output, (array_key_exists($token, $config) ? $config[$token] : $token) . " ");
  }
  fwrite($output, "\n");
}
#-----------------------------

// @@PLEAC@@_2.0
// As is the case under so many other languages floating point use under PHP is fraught
// with dangers. Although the basic techniques shown below are valid, please refer to
// the official PHP documentation for known issues, bugs, and alternate approaches 

// @@PLEAC@@_2.1
// Two basic approaches to numeric validation:
// * Built-in functions like 'is_numeric', 'is_int', 'is_float' etc
// * Regexes, as shown below

$s = '12.345';

preg_match('/\D/', $s) && die("has nondigits\n");
preg_match('/^\d+$/', $s) || die("not a natural number\n");
preg_match('/^-?\d+$/', $s) || die("not an integer\n");
preg_match('/^[+-]?\d+$/', $s) || die("not an integer\n");
preg_match('/^-?\d+\.?\d*$/', $s) || die("not a decimal\n");
preg_match('/^-?(?:\d+(?:\.\d*)?|\.\d+)$/', $s) || die("not a decimal\n");
preg_match('/^([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/', $s) || die("not a C float\n");

// ----------------------------

function getnum($s)
{
  sscanf($s, "%D", $number); return isset($number) ? $number : 0;
}

echo getnum(123) . "\n";   // ok
echo getnum(0xff) . "\n";  // ..
echo getnum(044) . "\n";   // ..

echo getnum('x') . "\n";   // fail

// @@PLEAC@@_2.2
// In PHP floating point comparisions are 'safe' [meaning the '==' comparison operator
// can be used] as long as the value consists of 14 digits or less [total digits, either
// side of the decimal point e.g. xxxxxxx.xxxxxxx, xxxxxxxxxxxxxx., .xxxxxxxxxxxxxx]. If
// values with more digits must be compared, then:
//
// * Represent as strings, and take care to avoid any implicit conversions e.g. don't pass
//   a float as a float to a function and expect all digits to be retained - they won't be -
//   then use 'strcmp' to compare the strings
//
// * Avoid float use; perhaps use arbitrary precision arithmetic. In this case, the
//   'bccomp' function is relevant

// Will work as long as each floating point value is 14 digits or less
if ($float_1 == $float_2)
{
  ; // ...
}

// Compare as strings
$cmp = strcmp('123456789.123456789123456789', '123456789.123456789123456788');

// Use 'bccomp'
$precision = 5; // Number of significant comparison digits after decimal point
if (bccomp('1.111117', '1.111116', $precision))
{
  ; // ...
}

$precision = 6;
if (bccomp('1.111117', '1.111116', $precision))
{
  ; // ...
}

// ----------------------------

$wage = 536;
$week = $wage * 40;
printf("One week's wage is: $%.2f\n", $week / 100);

// @@PLEAC@@_2.3
// Preferred approach
$rounded = round($unrounded, $precision);

// Possible alternate approach
$format = '%[width].[prec]f';
$rounded = sprintf($format, $unrounded);

// ------------

$a = 0.255; $b = round($a, 2);
echo "Unrounded: {$a}\nRounded: {$b}\n";

$a = 0.255; $b = sprintf('%.2f', $a);
echo "Unrounded: {$a}\nRounded: {$b}\n";

$a = 0.255;
printf("Unrounded: %.f\nRounded: %.2f\n", $a, $a);

// ----------------------------

echo "number\tint\tfloor\tceil\n";

foreach(array(3.3, 3.5, 3.7, -3.3) as $number)
{
  printf("%.1f\t%.1f\t%.1f\t%.1f\n", $number, (int) $number, floor($number), ceil($number));
}

// @@PLEAC@@_2.4
// PHP offers the 'bindec' and 'decbin' functions to converting between binary and decimal

$num = bindec('0110110');

$binstr = decbin(54);

// @@PLEAC@@_2.5
foreach (range($X, $Y) as $i)
{
  ; // ...
}

foreach (range($X, $Y, 7) as $i)
{
  ; // ...
}

for ($i = $X; $i <= $Y; $i++)
{
  ; // ...
}

for ($i = $X; $i <= $Y; $i += 7)
{
  ; // ...
}

// ----------------------------

echo 'Infancy is:'; foreach(range(0, 2) as $i) echo " {$i}\n";
echo 'Toddling is:'; foreach(range(3, 4) as $i) echo " {$i}\n";
echo 'Childhood is:'; foreach(range(5, 12) as $i) echo " {$i}\n";

// @@PLEAC@@_2.6
// PHP offers no native support for Roman Numerals. However, a 'Numbers_Roman' class
// is available for download from PEAR: [http://pear.php.net/package/Numbers_Roman].
// Note the following 'include' directives are required:
//
//   include_once('Numbers/Roman.php');

$roman = Numbers_Roman::toNumeral($arabic);
$arabic = Numbers_Roman::toNumber($roman);

// ----------------------------

$roman_fifteen = Numbers_Roman::toNumeral(15);

$arabic_fifteen = Numbers_Roman::toNumber($roman_fifteen);

printf("Roman for fifteen is: %s\n", $roman_fifteen);
printf("Arabic for fifteen is: %d\n", $arabic_fifteen);

// @@PLEAC@@_2.7
// Techniques used here simply mirror Perl examples, and are not an endorsement
// of any particular RNG technique

// In PHP do this ...
$random = rand($lowerbound, $upperbound);
$random = rand($x, $y);

// ----------------------------

function make_password($chars, $reqlen)
{
  $len = strlen($chars);
  for ($i = 0; $i < $reqlen; $i++) $password .= substr($chars, rand(0, $len), 1);
  return $password;
}

$chars = 'ABCDEfghijKLMNOpqrstUVWXYz'; $reqlen = 8;

$password = make_password($chars, $reqlen);

// @@PLEAC@@_2.8
// PHP sports a large number of C Standard Library routines including the 'srand'
// function, used to re-seed the RNG used with calls to the 'rand' function. Thus,
// as per Perl example:

while (TRUE)
{
  $seed = (int) fgets(STDIN);
  if (!empty($seed)) break;
}

srand($seed);

// @@PLEAC@@_2.9
// The above is considered - for many reasons - a poor way of seeding the RNG. PHP
// also offers alternate versions of the functions, 'mt_srand' and 'mt_rand',
// which are described as faster, and more 'random', though key to obtaining a
// more 'random' distribution of generated numbers seems to be through using
// a combination of a previously saved random value in combination with an
// unrepeatable value [like the current time in microseconds] that is multiplied
// by a large prime number, or perhaps as part of a hash [examples available in
// PHP documentation for 'srand' and 'mt_srand']

mt_srand($saved_random_value + microtime() * 1000003);

// or

mt_srand(($saved_random_value + hexdec(substr(md5(microtime()), -8))) & 0x7fffffff);

// Use of 'mt_rand' together with an appropriate seeding approach should help better
// approximate the generation of a 'truly random value'
$truly_random_value = mt_rand();

// @@PLEAC@@_2.10
function random() { return (float) rand() / (float) getrandmax(); }

function gaussian_rand()
{
  $u1 = 0.0; $u2 = 0.0; $g1 = 0.0; $g2 = 0.0; $w = 0.0;
  
  do
  {
    $u1 = 2.0 * random() - 1.0; $u2 = 2.0 * random() - 1.0;
    $w = $u1 * $u1 + $u2 * $u2;
  } while ($w > 1.0);
  
  $w = sqrt((-2.0 * log($w)) / $w); $g2 = $u1 * $w; $g1 = $u2 * $w;

  return $g1;
}

// ------------

$mean = 25.0; $sdev = 2.0;
$salary = gaussian_rand() * $mean + $sdev;

printf("You have been hired at: %.2f\n", $salary);

// @@PLEAC@@_2.11
// 'deg2rad' and 'rad2deg' are actually PHP built-ins, but here is how you might implement
/  them if needed
function deg2rad_($deg) { return ($deg / 180.0) * M_PI; }
function rad2deg_($rad) { return ($rad / M_PI) * 180.0; }

// ------------

printf("%f\n", deg2rad_(180.0));
printf("%f\n", deg2rad(180.0));

// ----------------------------

function degree_sin($deg) { return sin(deg2rad($deg)); }

// ------------

$rad = deg2rad(380.0);

printf("%f\n", sin($rad));
printf("%f\n", degree_sin(380.0));

// @@PLEAC@@_2.12
function my_tan($theta) { return sin($theta) / cos($theta); }

// ------------

$theta = 3.7;

printf("%f\n", my_tan($theta));
printf("%f\n", tan($theta));

// @@PLEAC@@_2.13
$value = 100.0;

$log_e = log($value);
$log_10 = log10($value);

// ----------------------------

function log_base($base, $value) { return log($value) / log($base); }

// ------------

$answer = log_base(10.0, 10000.0);

printf("log(10, 10,000) = %f\n", $answer);

// @@PLEAC@@_2.14
// PHP offers no native support for matrices. However, a 'Math_Matrix' class
// is available for download from PEAR: [http://pear.php.net/package/Math_Matrix].
// Note the following 'include' directives are required:
//
//  include_once('Math/Matrix.php');

$a = new Math_Matrix(array(array(3, 2, 3), array(5, 9, 8)));
$b = new Math_Matrix(array(array(4, 7), array(9, 3), array(8, 1)));

echo $a->toString() . "\n";
echo $b->toString() . "\n";

// NOTE: When I installed this package I had to rename the 'clone' method else
// it would not load, so I chose to rename it to 'clone_', and this usage is
// shown below. This bug may well be fixed by the time you obtain this package

$c = $a->clone_();
$c->multiply($b);

echo $c->toString() . "\n";

// @@PLEAC@@_2.15
// PHP offers no native support for complex numbers. However, a 'Math_Complex' class
// is available for download from PEAR: [http://pear.php.net/package/Math_Complex].
// Note the following 'include' directives are required:
//
//   include_once('Math/Complex.php');
//   include_once('Math/TrigOp.php');
//   include_once('Math/ComplexOp.php');

$a = new Math_Complex(3, 5);
$b = new Math_Complex(2, -2);

$c = Math_ComplexOp::mult($a, $b);

echo $c->toString() . "\n";

// ----------------------------

$d = new Math_Complex(3, 4);
$r = Math_ComplexOp::sqrt($d);

echo $r->toString() . "\n";

// @@PLEAC@@_2.16
// Like C, PHP supports decimal-alternate notations. Thus, for example, the integer
// value, 867, is expressable in literal form as:
//
//   Hexadecimal -> 0x363
//   Octal       -> 01543
//
// For effecting such conversions using strings there is 'sprintf' and 'sscanf'.

$dec = 867;
$hex = sprintf('%x', $dec);
$oct = sprintf('%o', $dec);

// ------------

$dec = 0;
$hex = '363';

sscanf($hex, '%x', $dec);

// ------------

$dec = 0;
$oct = '1543';

sscanf($oct, '%o', $dec);

// ----------------------------

$number = 0;

printf('Gimme a number in decimal, octal, or hex: ');
sscanf(fgets(STDIN), '%D', $number);

printf("%d %x %o\n", $number, $number, $number);

// @@PLEAC@@_2.17
// PHP offers the 'number_format' built-in function to, among many other format tasks, 
// commify numbers. Perl-compatible [as well as extended] regexes are also available

function commify_series($s) { return number_format($s, 0, '', ','); }

// ------------

$hits = 3456789;

printf("Your website received %s accesses last month\n", commify_series($hits));

// ----------------------------

function commify($s)
{
  return strrev(preg_replace('/(\d\d\d)(?=\d)(?!\d*\.)/', '${1},', strrev($s)));
}

// ------------

$hits = 3456789;

echo commify(sprintf("Your website received %d accesses last month\n", $hits));

// @@PLEAC@@_2.18
function pluralise($value, $root, $singular='' , $plural='s')
{
  return $root . (($value > 1) ? $plural : $singular);
}

// ------------

$duration = 1;
printf("It took %d %s\n", $duration, pluralise($duration, 'hour'));
printf("%d %s %s enough.\n", $duration, pluralise($duration, 'hour'),
      pluralise($duration, '', 'is', 'are'));

$duration = 5;
printf("It took %d %s\n", $duration, pluralise($duration, 'hour'));
printf("%d %s %s enough.\n", $duration, pluralise($duration, 'hour'),
      pluralise($duration, '', 'is', 'are'));

// ----------------------------

function plural($singular)
{
  $s2p = array('/ss$/' => 'sses', '/([psc]h)$/' => '${1}es', '/z$/' => 'zes',
               '/ff$/' => 'ffs', '/f$/' => 'ves', '/ey$/' => 'eys',
               '/y$/' => 'ies', '/ix$/' => 'ices', '/([sx])$/' => '$1es',
               '$' => 's');

  foreach($s2p as $s => $p)
  {
    if (preg_match($s, $singular)) return preg_replace($s, $p, $singular);
  }
}

// ------------

foreach(array('mess', 'index', 'leaf', 'puppy') as $word)
{
  printf("%6s -> %s\n", $word, plural($word));
}

// @@PLEAC@@_2.19
// @@INCOMPLETE@@
// @@INCOMPLETE@@

// @@PLEAC@@_3.0
// PHP's date / time suport is quite extensive, and appears grouped into three areas of
// functionality:
//
// * UNIX / C Library [libc]-based routines, which include [among others]:
//   - localtime, gmtime
//   - strftime, strptime, mktime
//   - time, getdate, gettimeofday, 
//
// * PHP 'native' functions, those date / time routines released in earlier versions,
//   and which otherwise provide 'convenience' functionality; these include:
//   - date
//   - strtotime
//
// * 'DateTime' class-based. This facility appears [according to the PHP documentation]
//   to be extremely new / experimental, so whilst usage examples will be provided, they
//   should not be taken to be 'official' examples, and obviously, subject to change.
//   My own impression is that this facility is currently only partially implemented,
//   so there is limited use for these functions. The functions included in this group
//   are some of the 'date_'-prefixed functions; they are, however, not used standalone,
//   but as methods in conjunction with an object. Typical usage:
//
//     $today = new DateTime();             // actually calls: date_create($today, ...);
//     echo $today->format('U') . "\n";     // actually calls: date_format($today, ...);
//
// Also worth mentioning is the PEAR [PHP Extension and Repository] package, 'Calendar',
// which offers a rich set of date / time manipulation facilities. However, since it is
// not currently shipped with PHP, no examples appear

// Helper functions for performing date arithmetic 

function dateOffset()
{
  static $tbl = array('sec' => 1, 'min' => 60, 'hou' => 3600, 'day' => 86400, 'wee' => 604800);
  $delta = 0;

  foreach (func_get_args() as $arg)
  {
    $kv = explode('=', $arg);
    $delta += $kv[1] * $tbl[strtolower(substr($kv[0], 0, 3))];
  }

  return $delta;
}

function dateInterval($intvltype, $timevalue)
{
  static $tbl = array('sec' => 1, 'min' => 60, 'hou' => 3600, 'day' => 86400, 'wee' => 604800);
  return (int) round($timevalue / $tbl[strtolower(substr($intvltype, 0, 3))]);
}

// ----------------------------

// Extract indexed array from 'getdate'
$today = getdate();
printf("Today is day %d of the current year\n", $today['yday']);

// Extract indexed, and associative arrays, respectively, from 'localtime'
$today = localtime();
printf("Today is day %d of the current year\n", $today[7]);

$today = localtime(time(), TRUE);
printf("Today is day %d of the current year\n", $today['tm_yday']);

// @@PLEAC@@_3.1
define(SEP, '-');

// ------------

$today = getdate();

$day = $today['mday'];
$month = $today['mon'];
$year = $today['year'];

// Either do this to use interpolation:
$sep = SEP;
echo "Current date is: {$year}{$sep}{$month}{$sep}{$day}\n";

// or simply concatenate:
echo 'Current date is: ' . $year . SEP . $month . SEP . $day . "\n";

// ------------

$today = localtime(time(), TRUE);

$day = $today['tm_mday'];
$month = $today['tm_mon'] + 1;
$year = $today['tm_year'] + 1900;

printf("Current date is: %4d%s%2d%s%2d\n", $year, SEP, $month, SEP, $day);

// ------------

$format = 'Y' . SEP . 'n' . SEP . 'd';

$today = date($format);

echo "Current date is: {$today}\n";

// ------------

$sep = SEP;

$today = strftime("%Y$sep%m$sep%d");

echo "Current date is: {$today}\n";

// @@PLEAC@@_3.2
$timestamp = mktime($hour, $min, $sec, $month, $day, $year);

$timestamp = gmmktime($hour, $min, $sec, $month, $day, $year);

// @@PLEAC@@_3.3
$dmyhms = getdate();            // timestamp: current date / time

$dmyhms = getdate($timestamp);  // timestamp: arbitrary

$day = $dmyhms['mday'];
$month = $dmyhms['mon'];
$year = $dmyhms['year'];

$hours = $dmyhms['hours'];
$minutes = $dmyhms['minutes'];
$seconds = $dmyhms['seconds'];

// @@PLEAC@@_3.4
// Date arithmetic is probably most easily performed using timestamps [i.e. *NIX Epoch
// Seconds]. Dates - in whatever form - are converted to timestamps, these are
// arithmetically manipulated, and the result converted to whatever form required.
// Note: use 'mktime' to create timestamps properly adjusted for daylight saving; whilst
// 'strtotime' is more convenient to use, it does not, AFAIK, include this adjustment

$when = $now + $difference;
$then = $now - $difference;

// ------------

$now = mktime(0, 0, 0, 8, 6, 2003);

$diff1 = dateOffset('day=1'); $diff2 = dateOffset('weeks=2');

echo 'Today is:                 ' . date('Y-m-d', $now) . "\n";
echo 'One day in the future is: ' . date('Y-m-d', $now + $diff1) . "\n";
echo 'Two weeks in the past is: ' . date('Y-m-d', $now - $diff2) . "\n";

// ----------------------------

// Date arithmetic performed using a custom function, 'dateOffset'. Internally, offset may
// be computed in one of several ways:
// * Direct timestamp manipulation - fastest, but no daylight saving adjustment 
// * Via 'date' built-in function - slower [?], needs a base time from which to
//   compute values, but has daylight saving adjustment 
// * Via 'strtotime' built-in function - as for 'date'
// * Via 'DateTime' class
//
// Approach used here is to utilise direct timestamp manipulation in 'dateOffset' [it's
// performance can also be improved by replacing $tbl with a global definition etc],
// and to illustrate how the other approaches might be used 

// 1. 'dateOffset'

$birthtime = mktime(3, 45, 50, 1, 18, 1973);

$interval = dateOffset('day=55', 'hours=2', 'min=17', 'sec=5');

$then = $birthtime + $interval;

printf("Birthtime is: %s\nthen is:      %s\n", date(DATE_RFC1123, $birthtime), date(DATE_RFC1123, $then));

// ------------

// 2. 'date'

// Base values, and offsets, respectively
$hr = 3; $min = 45; $sec = 50; $mon = 1; $day = 18; $year = 1973;

$yroff = 0; $monoff = 0; $dayoff = 55; $hroff = 2; $minoff = 17; $secoff = 5;

// Base date
$birthtime = mktime($hr, $min, $sec, $mon, $day, $year, TRUE);

$year = date('Y', $birthtime) + $yroff;
$mon = date('m', $birthtime) + $monoff;
$day = date('d', $birthtime) + $dayoff;

$hr = date('H', $birthtime) + $hroff;
$min = date('i', $birthtime) + $minoff;
$sec = date('s', $birthtime) + $secoff;

// Offset date
$then = mktime($hr, $min, $sec, $mon, $day, $year, TRUE);

printf("Birthtime is: %s\nthen is:      %s\n", date(DATE_RFC1123, $birthtime), date(DATE_RFC1123, $then));

// ------------

// 3. 'strtotime'

// Generate timestamp whatever way is preferable
$birthtime = mktime(3, 45, 50, 1, 18, 1973);
$birthtime = strtotime('1/18/1973 03:45:50');

$then = strtotime('+55 days 2 hours 17 minutes 2 seconds', $birthtime);

printf("Birthtime is: %s\nthen is:      %s\n", date(DATE_RFC1123, $birthtime), date(DATE_RFC1123, $then));

// ------------

// 4. 'DateTime' class

$birthtime = new DateTime('1/18/1973 03:45:50');
$then = new DateTime('1/18/1973 03:45:50');
$then->modify('+55 days 2 hours 17 minutes 2 seconds');

printf("Birthtime is: %s\nthen is:      %s\n", $birthtime->format(DATE_RFC1123), $then->format(DATE_RFC1123));

// @@PLEAC@@_3.5
// Date intervals are most easily computed using timestamps [i.e. *NIX Epoch
// Seconds] which, of course, gives the interval result is seconds from which
// all other interval measures [days, weeks, months, years] may be derived.
// Refer to previous section for discussion of daylight saving and other related
// problems

$interval_seconds = $recent - $earlier;

// ----------------------------

// Conventional approach ...
$bree = strtotime('16 Jun 1981, 4:35:25');
$nat = strtotime('18 Jan 1973, 3:45:50');

// ... or, with daylight saving adjustment
$bree = mktime(4, 35, 25, 6, 16, 1981, TRUE);
$nat = mktime(3, 45, 50, 1, 18, 1973, TRUE);

$difference = $bree - $nat;

// 'dateInterval' custom function computes intervals in several measures given an
// interval in seconds. Note, 'month' and 'year' measures not provided
printf("There were %d seconds between Nat and Bree\n", $difference);
printf("There were %d weeks between Nat and Bree\n", dateInterval('weeks', $difference));
printf("There were %d days between Nat and Bree\n", dateInterval('days', $difference));
printf("There were %d hours between Nat and Bree\n", dateInterval('hours', $difference));
printf("There were %d minutes between Nat and Bree\n", dateInterval('mins', $difference));

// @@PLEAC@@_3.6
// 'getdate' accepts a timestamp [or implicitly calls 'time'] and returns an array of
// date components. It returns much the same information as 'strptime' except that
// the component names are different

$today = getdate();

$weekday = $today['wday'];
$monthday = $today['mday'];
$yearday = $today['yday'];

$weeknumber = (int) round($yearday / 7.0);

// Safter method of obtaining week number
$weeknumber = strftime('%U') + 1;

// ----------------------------

define(SEP, '/');

$day = 16;
$month = 6;
$year = 1981;

$timestamp = mktime(0, 0, 0, $month, $day, $year);

$date = getdate($timestamp);

$weekday = $date['wday'];
$monthday = $date['mday'];
$yearday = $date['yday'];

$weeknumber = (int) round($yearday / 7.0);

$weeknumber = strftime('%U', $timestamp) + 1;

// Interpolate ...
$sep = SEP;
echo "{$month}{$sep}{$day}{$sep}{$year} was a {$date['weekday']} in week {$weeknumber}\n";

// ... or, concatenate
echo $month . SEP . $day . SEP . $year . ' was a ' . $date['weekday']
     . ' in week ' . $weeknumber . "\n";

// @@PLEAC@@_3.7
// 'strtotime' parses a textual date expression by attempting a 'best guess' at
// the format, and either fails, or generates a timestamp. Timestamp could be fed
// into any one of the various functions; example:
$timestamp = strtotime('1998-06-03'); echo strftime('%Y-%m-%d', $timestamp) . "\n";

// 'strptime' parses a textual date expression according to a specified format,
// and returns an array of date components; components can be easily dumped
print_r(strptime('1998-06-03', '%Y-%m-%d'));

// ----------------------------

// Parse date string according to format
$darr = strptime('1998-06-03', '%Y-%m-%d');

if (!empty($darr))
{
  // Show date components in 'debug' form
  print_r($darr);

  // Check whether there was a parse error i.e. one or more components could not
  // be extracted from the string
  if (empty($darr['unparsed']))
  {
    // Properly parsed date, so validate required components using, 'checkdate'
    if (checkdate($darr['tm_mon'] + 1, $darr['tm_mday'], $darr['tm_year'] + 1900))
      echo "Parsed date verified as correct\n";
    else
      echo "Parsed date failed verification\n";
  }
  else
  {
    echo "Date string parse not complete; failed components: {$darr['unparsed']}\n";
  }
}
else
{
  echo "Date string could not be parsed\n";
}

// @@PLEAC@@_3.8
// 'date' and 'strftime' both print a date string based on:
// * Format String, describing layout of date components
// * Timestamp [*NIX Epoch Seconds], either given explicitly, or implictly
//   via a call to 'time' which retrieves current time value

$ts = 1234567890;

date('Y/m/d', $ts); 
date('Y/m/d', mktime($h, $m, $s, $mth, $d, $y, $is_dst)); 

date('Y/m/d');         // same as: date('Y/m/d', time());

// ------------

$ts = 1234567890;

strftime('%Y/%m/%d', $ts);
strftime('%Y/%m/%d', mktime($h, $m, $s, $mth, $d, $y, $is_dst));

strftime('%Y/%m/%d');  // same as: strftime('%Y/%m/%d', time());

// ----------------------------

// 'mktime' creates a local time timestamp
$t = strftime('%a %b %e %H:%M:%S %z %Y', mktime(3, 45, 50, 1, 18, 73, TRUE));
echo "{$t}\n";

// 'gmmktime' creates a GMT time timestamp
$t = strftime('%a %b %e %H:%M:%S %z %Y', gmmktime(3, 45, 50, 1, 18, 73));
echo "{$t}\n";

// ----------------------------

// 'strtotime' parses a textual date expression, and generates a timestamp 
$t = strftime('%A %D', strtotime('18 Jan 1973, 3:45:50'));
echo "{$t}\n";

// This should generate output identical to previous example
$t = strftime('%A %D', mktime(3, 45, 50, 1, 18, 73, TRUE));
echo "{$t}\n";

// @@PLEAC@@_3.9
// PHP 5 and above can use the built-in, 'microtime'. Crude implementation for ealier versions:
// function microtime() { $t = gettimeofday(); return (float) ($t['sec'] + $t['usec'] / 1000000.0); } 

// ------------

$before = microtime();

$line = fgets(STDIN);

$elapsed = microtime() - $before;

printf("You took %.3f seconds\n", $elapsed);

// ------------

define(NUMBER_OF_TIMES, 100);
define(SIZE, 500);

for($i = 0; $i < NUMBER_OF_TIMES; $i++)
{
  $arr = array();
  for($j = 0; $j < SIZE; $j++) $arr[] = rand();

  $begin = microtime();
  sort($arr);
  $elapsed = microtime() - $begin;

  $total_time += $elapsed;
}

printf("On average, sorting %d random numbers takes %.5f seconds\n", SIZE, $total_time / (float) NUMBER_OF_TIMES);

// @@PLEAC@@_3.10
// Low-resolution: sleep time specified in seconds
sleep(1);

// High-resolution: sleep time specified in microseconds [not reliable under Windows]
usleep(250000);

// @@PLEAC@@_3.11
// @@INCOMPLETE@@
// @@INCOMPLETE@@

// @@PLEAC@@_4.0
// Nested arrays are supported, and may be easily printed using 'print_r'

$nested = array('this', 'that', 'the', 'other');

$nested = array('this', 'that', array('the', 'other')); print_r($nested);

$tune = array('The', 'Star-Spangled', 'Banner');

// @@PLEAC@@_4.1
// PHP offers only the 'array' type which is actually an associative array, though
// may be numerically indexed, to mimic vectors and matrices; there is no separate
// 'list' type

$a = array('quick', 'brown', 'fox');

// ------------

$a = escapeshellarg('Why are you teasing me?');

// ------------

$lines = <<<END_OF_HERE_DOC
    The boy stood on the burning deck,
    it was as hot as glass.
END_OF_HERE_DOC;

// ------------

$bigarray = array_map('rtrim', file('mydatafile'));

// ------------

$banner = 'The mines of Moria';

$banner = escapeshellarg('The mines of Moria');

// ------------

$name = 'Gandalf';

$banner = "Speak {$name}, and enter!";

$banner = 'Speak ' . escapeshellarg($name) . ' and welcome!';

// ------------

$his_host = 'www.perl.com';

$host_info = `nslookup $his_host`;

$cmd = 'ps ' . posix_getpid(); $perl_info = `$cmd`;

$shell_info = `ps $$`;

// ------------

$banner = array('Costs', 'only', '$4.95');

$banner = array_map('escapeshellarg', split(' ', 'Costs only $4.95'));

// ------------

// AFAIK PHP doesn't support non-quoted strings ala Perl's 'q', 'qq' and 'qw', so arrays
// created from strings must use quoted strings, and make use of 'split' [or equivalent].
// A slew of functions exist for performing string quoting, including 'escapeshellarg',
// 'quotemeta', and 'preg_quote'

$brax = split(' ', '( ) < > { } [ ]');

// Do this to quote each element within '..'
// $brax = array_map('escapeshellarg', split(' ', '( ) < > { } [ ]'));

$rings = split(' ', 'Nenya Narya Vilya');

$tags = split(' ', 'LI TABLE TR TD A IMG H1 P');

$sample = split(' ', 'The vertical bar | looks and behaves like a pipe.');

// @@PLEAC@@_4.2
function commify_series($list)
{
  $n = str_word_count($list); $series = str_word_count($list, 1);

  if ($n == 0) return NULL;
  if ($n == 1) return $series[0];
  if ($n == 2) return $series[0] . ' and ' . $series[1];
  
  return join(', ', array_slice($series, 0, -1)) . ', and ' . $series[$n - 1];
}

// ------------

echo commify_series('red') . "\n";
echo commify_series('red yellow') . "\n";
echo commify_series('red yellow green') . "\n";

$mylist = 'red yellow green';
echo 'I have ' . commify_series($mylist) . " marbles.\n";

// ----------------------------

function commify_series($arr)
{
  $n = count($arr); $sepchar = ',';

  foreach($arr as $str)
  {
    if (strpos($str, ',') === false) continue;
    $sepchar = ';'; break; 
  }

  if ($n == 0) return NULL;
  if ($n == 1) return $arr[0];
  if ($n == 2) return $arr[0] . ' and ' . $arr[1];
  
  return join("{$sepchar} ", array_slice($arr, 0, -1)) . "{$sepchar} and " . $arr[$n - 1];
}

// ------------

$lists = array(
  array('just one thing'),
  split(' ', 'Mutt Jeff'),
  split(' ', 'Peter Paul Mary'),
  array('To our parents', 'Mother Theresa', 'God'),
  array('pastrami', 'ham and cheese', 'peanut butter and jelly', 'tuna'),
  array('recycle tired, old phrases', 'ponder big, happy thoughts'),
  array('recycle tired, old phrases', 'ponder big, happy thoughts', 'sleep and dream peacefully'));

foreach($lists as $arr)
{
  echo 'The list is: ' . commify_series($arr) . ".\n";
}

// @@PLEAC@@_4.3
// AFAICT you cannot grow / shrink an array to an arbitrary size. However, you can:
// * Grow an array by appending an element using subscrip notation, or using
//   either 'array_unshift' or 'array_push' to add one or more elements

$arr[] = 'one';
array_unshift($arr, 'one', 'two', 'three');
array_push($arr, 'one', 'two', 'three');

// * Shrink an array by using 'unset' to remove one or more specific elements, or
//   either 'array_shift' or 'array_pop' to remove an element from the ends

unset($arr[$idx1], $arr[$idx2], $arr[$idx3]);
$item = array_shift($arr);
$item = array_pop($arr);

// ----------------------------

function what_about_the_array()
{
  global $people;

  echo 'The array now has ' . count($people) . " elements\n";
  echo 'The index value of the last element is ' . (count($people) - 1) . "\n";
  echo 'Element #3 is ' . $people[3] . "\n";
}

$people = array('Crosby', 'Stills', 'Nash', 'Young');
what_about_the_array();

array_pop($people);
what_about_the_array();

// Cannot, AFAICT, resize the array to an arbitrary size

# @@PLEAC@@_4.4
foreach ($list as $item) {
    // do something with $item
}

// Environment listing example

// PHP defines a superglobal $_ENV to provide access to environment
// variables.

// Beware, array assignment means copying in PHP. You need to use
// the reference operator to avoid copying. But we want a copy here.
$env = $_ENV;

// PHP can sort an array by key, so you don't need to get keys,
// and then sort.
ksort($env);

foreach ($env as $key => $value) {
    echo "{$key}={$value}\n";
}

// Literal translation of Perl example would be:
$keys = array_keys($_ENV);
sort($keys);
foreach ($keys as $key) {
    echo "{$key}={$_ENV[$key]}\n";
}

// This assumes that MAX_QUOTA is a named constant.
foreach ($all_users as $user) {
    $disk_space = get_usage($user);
    if ($disk_space > MAX_QUOTA) {
        complain($user);
    }
}

// You can't modify array's elements in-place.
$array = array(1, 2, 3);
$newarray = array();
foreach ($array as $item) {
    $newarray[] = $item - 1;
}
print_r($newarray);

// Before PHP 5, that is. You can precede the reference operator
// before $item to get reference instead of copy.
$array = array(1, 2, 3);
foreach ($array as &$item) {
    $item--;
}
print_r($array);

// TODO: explain the old each() and list() iteration construct.
// foreach is new in PHP 4, and there are subtle differences.

// @@PLEAC@@_4.5
// Conventional 'read-only' access
foreach($array as $item)
{
  ; // Can access, but not update, array element referred to by '$item'
}

// ----

// '&' makes '$item' a reference
foreach($array as &$item)
{
  ; // Update array element referred to by '$item'
}

// ------------

$arraylen = count($array);

for($i = 0; $i < $arraylen; $i++)
{
  ; // '$array' is updateable via subscript notation
}

// ----------------------------

$fruits = array('Apple', 'Raspberry');

foreach($fruits as &$fruit)
{
  echo "{$fruit} tastes good in a pie.\n";
}

$fruitlen = count($fruits);

for($i = 0; $i < $fruitlen; $i++)
{
  echo "{$fruits[$i]} tastes good in a pie.\n";
}

// ----------------------------

$rogue_cats = array('Blackie', 'Goldie', 'Silkie');

// Take care to assign reference to '$rogue_cats' array via '=&'
$namelist['felines'] =& $rogue_cats;

// Take care to make '$cat' a reference via '&$' to allow updating
foreach($namelist['felines'] as &$cat)
{
  $cat .= ' [meow]';
}

// Via array reference
foreach($namelist['felines'] as $cat)
{
  echo "{$cat} purrs hypnotically.\n";
}

echo "---\n";

// Original array
foreach($rogue_cats as $cat)
{
  echo "{$cat} purrs hypnotically.\n";
}

// @@PLEAC@@_4.6
// PHP offers the 'array_unique' function to perform this task. It works with both keyed,
// and numerically-indexed arrays; keys / indexes are preserved; use of 'array_values' 
// is recommended to reindex numerically-indexed arrays since there will likely be missing
// indexes

// Remove duplicate values
$unique = array_unique($array);

// Remove duplicates, and reindex [for numerically-indexed arrays only]
$unique = array_values(array_unique($array));

// or use:
$unique = array_keys(array_flip($array));

// ----------------------------

// Selected Perl 'seen' examples
foreach($list as $item)
{
  if (!isset($seen[$item]))
  {
    $seen[$item] = TRUE;
    $unique[] = $item;
  }
}

// ------------

foreach($list as $item)
{
  $seen[$item] || (++$seen[$item] && ($unique[] = $item));
}

// ------------

function some_func($item)
{
  ; // Do something with '$item'
}

foreach($list as $item)
{
  $seen[$item] || (++$seen[$item] && some_func($item));
}

// ----------------------------

foreach(array_slice(preg_split('/\n/', `who`), 0, -1) as $user_entry)
{
  $user = preg_split('/\s/', $user_entry);
  $ucnt[$user[0]]++;
}

ksort($ucnt);

echo "users logged in:\n";

foreach($ucnt as $user => $cnt)
{
  echo "\t{$user} => {$cnt}\n";
}

// @@PLEAC@@_4.7
// PHP offers the 'array_diff' and 'array_diff_assoc' functions to perform this task. Same
// points as made about 'array_unique' apply here also

$a = array('c', 'a', 'b', 'd');
$b = array('c', 'a', 'b', 'e');

$diff = array_diff($a, $b);                 // $diff -> [3] 'd'
$diff = array_diff($b, $a);                 // $diff -> [3] 'e'

// Numerically-indexed array, reindexed
$diff = array_values(array_diff($a, $b));   // $diff -> [0] 'd'
$diff = array_values(array_diff($b, $a));   // $diff -> [0] 'e'

// ----------------------------

// 1st Perl 'seen' example only

$a = array('k1' => 11, 'k2' => 12, 'k4' => 14);
$b = array('k1' => 11, 'k2' => 12, 'k3' => 13);

foreach($b as $item => $value) { $seen[$item] = 1; }

// Stores key only e.g. $aonly[0] contains 'k4', same as Perl example
foreach($a as $item => $value) { if (!$seen[$item]) $aonly[] = $item; }

// Stores key and value e.g. $aonly['k4'] contains 14, same entry as in $a
foreach($a as $item => $value) { if (!$seen[$item]) $aonly[$item] = $value; }

// ----------------------------

// Conventional way: $hash = array('key1' => 1, 'key2' => 2);

$hash['key1'] = 1;
$hash['key2'] = 2;

$hash = array_combine(array('key1', 'key2'), array(1, 2));

// ------------

$seen = array_slice($b, 0);

$seen = array_combine(array_keys($b), array_fill(0, count($b), 1));

// @@PLEAC@@_4.8
// PHP offers a number of array-based 'set operation' functions:
// * union:        array_unique(array_merge(...))
// * intersection: array_intersect and family
// * difference:   array_diff and family
// which may be used for this type of task. Also, if returned arrays need to be
// reindexed, 'array_slice($array, 0)', or 'array_values($array)' are useful

$a = array(1, 3, 5, 6, 7, 8);
$b = array(2, 3, 5, 7, 9);

$union = array_values(array_unique(array_merge($a, $b))); // 1, 2, 3, 5…