$re = '/<tem:AccessCode>(.*?)<\/tem:AccessCode>/m';
$str = '<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:tem="http://tempuri.org/">
<soap:Header/>
<soap:Body>
<tem:GetToken>
<tem:WebChanelID>8</tem:WebChanelID>
<tem:AccessCode>444555</tem:AccessCode>
</tem:GetToken>
</soap:Body>
</soap:Envelope>';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($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