- preg_match: documentation ( source)
- print_r: documentation ( source)
<?php
$myinput = 'test <span>1234</span><span>12345</span>test<span>5678</span><span>12345</span>test';
preg_match("/(<span>\d{4}<\/span>)/", $myinput, $myoutput);
print_r($myoutput);