转义方括号内的正则表达式

I'm trying to escape a parenthesis inside square brackets.

$pattern = "/^[a-zA-Z0-9 _-\(]{1,25}$/";
$str = "TEST (ok)";

if (preg_match($pattern, $str)) {
    echo "<br />OK";
} else {
    echo "<br />FAIL";
}

This give me the warning:

Warning: preg_match(): Compilation failed: range out of order in character class at offset 15 in /var/www/test.php on line 6
FAIL

Outside the square brackets the escaping works fine.

Any ideas?

You need to escape the hyphen as well...as written, it will match from the underscore (ASCII 95) through the left paren (ASCII 40).

escape the hyphen or move it to the front or back of the char class list