$re = '/( xmlns:?[^=]*=[""][^""]*[""])/';
$str = '<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<soap:Body>
<ConnectResponse xmlns="aa">
<ConnectResult xmlns="bb">
<RETURNS>
<STATUS>A92A7EBEE897499fA8B06D5FE94B8A30</STATUS>
<APIPAYLOAD>
<COMMAND>
<TRACKINGID mya="cc">e3d1618b4b7847628b10d4a432ec9151</TRACKINGID>
</COMMAND>
</APIPAYLOAD>
</RETURNS>
</ConnectResult>
</ConnectResponse>
</soap:Body>
</soap:Envelope>';
preg_match_all($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