- preg_replace: documentation ( source)
<?php
$pattern = "/^[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+\.[a-zA-Z.]{2,5}$/";
$pattern = "/^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,4})$/";
$replacement = "**************";
echo preg_replace($pattern, $replacement, "I want to replace this.is@an.email.address with stars");
echo preg_replace("/a/", "A", "I want to capitalise all A's");