- var_dump: documentation ( source)
- preg_match_all: documentation ( source)
<?php
$attrPattern = '/([a-z0-9-]*)(=(["\']??)([^"\']*?)\\3)?/siU';
$attr = 'target="_parent" data-foo data-bar="baz"';
preg_match_all($attrPattern, $attr, $matches, PREG_SET_ORDER);
var_dump($matches);