- preg_match: documentation ( source)
- print_r: documentation ( source)
<?php
// example code
$content = 'dasdasdas d asdas dasdas dasd [gallery ids="2727,2726,2721"] dasd as ads';
/*$ids = substr(strstr($content, '[gallery ids='), 14);
$ids = substr($ids, 0, strpos( $ids, '"]'));
$ids = explode(',', $ids);*/
$ids = preg_match($ids, '/?<=\[gallery ids")(.*\n?)(?="]/');
echo print_r($ids);