$re = '/data\.(?:test\w*|new)?(?:ID)?=([^,]+)/mi';
$str = 'data.testID=abd.123,
data.newID=abc.123.123,
data.testcaseID=abc.1_2,
data.testid=abc.123,
data.TestCaseID=abc.1.2,';
preg_match_all($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