$re = '/_name=(?:[^"]*"){3}/';
$str = '_name=aVlTcWRjVG1YeDhucWdEbVFrN3pSOHZ5QTRjOEJZZmZUZXNIYW1PV2RGOWYrczBhVWRmdVJTMUxYazVBOE8zQ3JNMmNVKzJLM2JJTzFON3FiLzFHUE0xY0pkdz09LS1jbkkwaWoxUUl3YVhMMkhtZHpaOW13PT0"%"3D--57356371d167f"foo"bar"';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php