$re = '/<tns:Name>CASE_ID<\/tns:Name>\s*<tns:Value>([^\<]+)/m';
$str = ' <tns:Name>CASE_ID</tns:Name> <tns:Value>pvm:0a12ne8f</tns:Value> </tns:Keys> ';
preg_match_all($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