$re = '/<abr:rules>((?!subapplication=).)*subapplication="(?!CM")[^"]+"((?!<\/abr:rules>).)*<\/abr:rules>/ms';
$str = '<abr:rules>
<abr:ruleTypeDefinition>
<abr:code>ADE</abr:code>
<abr:ownership>
<abr:owner organization="NT" application="DCS" subapplication="AM"/>
...lines...
...........
</abr:rules>
<abr:rules>
<abr:ruleTypeDefinition>
<abr:code>ADE</abr:code>
<abr:ownership>
<abr:owner organization="NT" application="DCS" subapplication="CM"/>
...lines...
...........
</abr:rules><abr:rules>
<abr:ruleTypeDefinition>
<abr:code>ABB</abr:code>
<abr:ownership>
<abr:owner organization="NT" application="DCS" subapplication="CM"/>
...lines...
...........
</abr:rules>
<abr:rules>
<abr:ruleTypeDefinition>
<abr:code>ADE</abr:code>
<abr:ownership>
<abr:owner organization="NT" application="DCS" subapplication="CM"/>
...lines...
...........
</abr:rules>';
preg_match_all($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