/todoist_backup.php

<?PHP
/// Simple Exporter for Todoist
/// Put API token in todoist_apitoken.txt file
ini_set('memory_limit', '-1');
set_time_limit(0);
error_reporting(-1);

// wrapper function for scraping API
function todoistAPICall($method, $arguments){
    global $base_url, $login_token;
    $arguments = is_null($arguments) ? array() : $arguments;
    return file_get_contents("{$base_url}/{$method}?token={$login_token}&".http_build_query($arguments));
}
// concatenate to output string
function backupConcat($string){
    global $backup;
    $backup = $backup.$string;
}
// token is found in Preferences>Account
$login_token = trim(file_get_contents("todoist_apitoken.txt"));
$base_url = "http://www.todoist.com/API";

$backup = "";
$projects_all = todoistAPICall("getProjects", null);
// Suboptimal, but decoding JSON can be troublesome for PHP
preg_match_all('|"id":(.+?)[}\s,]|is', $projects_all, $matches);
backupConcat("### PROJECTS, TASKS, and LABELS ###\n");
foreach($matches[1] as $project_id){
    $project_id = trim($project_id);
    backupConcat("### PROJECT ###\n");
    backupConcat(todoistAPICall('getProject', array('project_id' => $project_id))."\n");
    backupConcat("\t### TASKS ###\n");
    backupConcat("\t".todoistAPICall('getUncompletedItems', array('project_id' => $project_id))."\n");
    backupConcat("\t".todoistAPICall('getCompletedItems', array('project_id' => $project_id))."\n");
    backupConcat("\t### LABELS ###\n");
    backupConcat("\t".todoistAPICall('getLabels', array('project_id' => $project_id))."\n");
}
$backup_time = date('YmdHis');
backupConcat("### BACKUP DONE {$backup_time} ###\n");
echo "### BACKUP DONE {$backup_time} ###\n";
// write output string to file
file_put_contents("todoistbackup_{$backup_time}.txt", $backup);
?>