$re = '/CDATA\[(?P<name1>[X]..)/';
$str = ' name="activationtype" type="string"><![CDATA[Activate]]></Property><Property name="Label" type="string"><![CDATA[r315107961a]]></Property><Property name="Description" type="string"><![CDATA[315107961 Verbreitung der Altersvorsorge 2015]]></Property><Property name="CommO" type="string"><![CDATA[XXX]]></Property><Property name="CommissioningCountry" type="string"><![CDATA[DEU--Germany]]></Property><Property name="groupname" type="string"><![CDATA[]]></Property><Property name="cluster" type="string"><![CDATA[Slo-V]]></Property><Property name="clientid"';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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