Check if a variable have only one letter or a specific string

Question

I have my variable $_GET['artist'] and I'd like to check:

1. if that variable have got only one letter, and this letter is from a to z (case sensitive, so A is not valid);
2. or if that variable is all or other

How can I check it with regex and preg_match() on PHP?

Answer 1

if (preg_match('/^([a-z]|all|other)$/', $_GET['artist']) === 1) {
    // True
}

Assuming all and other should also be case sensitive.

Answer 2

function check($str){
    $c=strlen($str)==1 ? ord($str) : 0;    // get the ascii code if it is a single character
    return ($c>=ord('a') && $c<=ord('z'))  // it is a single character between a and z
        || strpos($str,'all')!==false      // it contains "all"
        || strpos($str,'other')!==false;   // it contains "other"
}

check($_GET['artist']);

See, no regex.

Edit: To humor our esteemed moderator, here goes the comments.

Edit 2: I wrote a little profile for both solutions, and here are the results:

Test    PHP                RegExp
a       0.11241698265076   0.16329884529114
other   0.15441918373108   0.17051410675049
all     0.11415100097656   0.16919803619385
al      0.14953303337097   0.16402912139893
// tested over 100k iterations (less TTC is better)

One can see who's the best when it comes to speed. Though I would personally opt for this one, there are certainly reasons why a regular expression would favorable. The facts are in place, and I just can't be bothered with this pointless argument.