$re = '/^(?=[^\/]*\/[^\/]*\/[^\/]*$).*/m';
$str = 'example.com/test/testurl
example.com/test/test-url
example.com/test/testurl/content
example.com/test/test-url/content';
$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