Search dates (yyyy-mm-dd) in a text file and increase these dates with n days (defaults to 1)

increase_date.php

<?php

if($argc < 2){
    echo "Usage: " . $argv[0] . " FILE [NUMDAYS]\n";
    return(1);
}
// Default to add 1 day
$daysToAdd = ($argc == 3) ? intval($argv[2]) : 1;
$text = file_get_contents($argv[1]);

$increase = function($match) use ($daysToAdd){
    try {
        $date = new DateTime($match[0]);
    } catch (Exception $e) {
        // Assume it was an invalid date, so just return the match
        return $match[0];
    }
    if($daysToAdd > 0){
        $date->add(new DateInterval('P'. $daysToAdd . 'D'));
    } else {
        $date->sub(new DateInterval('P'. abs($daysToAdd) . 'D'));
    }
    return $date->format('Y-m-d');
};

$replaced = preg_replace_callback('|(\d{4}-\d{2}-)(\d{2})|', $increase,$text);

file_put_contents($argv[1], $replaced);

return(0);
?>