$re = '/(?<!test(?:\w|\s)*\W{0,14})test/mi';
$str = 'Lorem ipsum Test sit amet, consectetur adipiscing elit. Vestibulum at erat ac enim malesuada pulvinar et nec ante. Cras erat ipsum, pellentesque vel volutpat ut, Test eu test. Test Quisque tincidunt varius mi. Suspendisse vitae lobortis diam. Vestibulum posuere massa id lectus faucibus posuere. Donec non sollicitudin est. Donec libero turpis, malesuada in Test';
preg_match_all($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