$re = '/<Cert>[\s\S]*?777[\s\S]*?<\/Cert>/';
$str = ' <Cert>
<ObjectID></ObjectID>
<PersonnelID>290164</PersonnelID>
<CertType>CX777G9T2</CertType>
<CertNumber>000000</CertNumber>
<Default>false</Default>
</Cert>
<Cert>
<ObjectID></ObjectID>
<PersonnelID>290164</PersonnelID>
<CertType>CX7a7G9T2</CertType>
<CertNumber>000000</CertNumber>
<Default>false</Default>
</Cert>';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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