- var_dump: documentation ( source)
- preg_filter: documentation ( source)
<?php
$input = "michael@test.com dave@cheese.mansions milkman@serverdouche.co.uk";
$email = preg_filter("/[-0-9a-zA-Z.+_]+@[-0-9a-zA-Z.+_]+\.[a-zA-Z]+/", $input);
var_dump($email);