preg_match_all + callbacks = preg_match_callback. No support for flags though.

preg_match_callback.php

<?php

function preg_match_callback($expression, $subject, $callback) {
    static $matches_count = 0;
    preg_replace_callback($expression, function($matches) use($callback) {
       call_user_func($callback, $matches);
    }, $subject, -1, $matches_count);
    return $matches_count;
}