<?php
$imageTag = <<< LOB
<img border="0" src="/images/image.jpg" alt="Image" width="100" height="100" />
<img border="0" src="/images/not_match_image.jpg" alt="Image" width="100" height="100" />
LOB;
preg_match('%<img.*?src=["\'](.*?)["\'].*?/>%i', $imageTag , $result); $foo = $result[1];
echo $foo;
PD9waHAKCiRpbWFnZVRhZyA9IDw8PCBMT0IKPGltZyBib3JkZXI9IjAiIHNyYz0iL2ltYWdlcy9pbWFnZS5qcGciIGFsdD0iSW1hZ2UiIHdpZHRoPSIxMDAiIGhlaWdodD0iMTAwIiAvPgo8aW1nIGJvcmRlcj0iMCIgc3JjPSIvaW1hZ2VzL25vdF9tYXRjaF9pbWFnZS5qcGciIGFsdD0iSW1hZ2UiIHdpZHRoPSIxMDAiIGhlaWdodD0iMTAwIiAvPgpMT0I7CgpwcmVnX21hdGNoKCclPGltZy4qP3NyYz1bIlwnXSguKj8pWyJcJ10uKj8vPiVpJywgJGltYWdlVGFnICwgJHJlc3VsdCk7CiRmb28gPSAkcmVzdWx0WzFdOwplY2hvICRmb287