PHP unindent

unindent.php

<?php
/**
 * Unindent a given string
 *
 * Empty lines are skipped.
 *
 * N.b.: de longest common substring is used, as a result all the
 * indenting has to be exactly the same. Proper unindenting may fail
 * otherwise.
 *
 * @param string $text
 * @return string
 */
function unindent($text) {
    if (preg_match('{\A[\r\n]*(\h+)[^\r\n]*+(?:[\r\n]++(?>\1[^\r\n]*+(?:[\r\n]+|\z)|[\r\n]+)+)?\z}', rtrim($text), $match)) {
        $text = preg_replace('{^' . $match[1] . '}m', '', $text);
    }

    return $text;
}