Function for normalizing Canadian postal codes is returning unexpected results

Question

I'm trying to normalize user input for Canadian postal codes.

The end goal is to get all input as A3A 3A3 - 7 characters, capitalized, with the first group letter number letter, second group as number letter number.

Users will sometimes use o or O for the number 0, or vice versa, so here is my function:

   $zip = htmlspecialchars($_REQUEST['zip']);
   if (!empty($zip)) {
       //if the format is A3A3A3, split it into two groups
        if (strlen($zip) == 6) {
            $zip = substr($zip, 0, 3) . " " . substr($zip, 3, 3);           
        }
       //now lets make sure there is only a empty space between groups
        if (strlen($zip) == 7) {
            $zip[3] = " ";
        }
       //let's put their o's, O's and 0's in the right places
        if ($zip[1] == ("O" || "o")) {
            $zip[1] = '0';
        }
        if ($zip[4] == ('O'||'o')) {
            $zip[4] = '0';
        }
        if ($zip[6] == ('O'||'o')) {
            $zip[6] = '0';
        }

        if ($zip[0] == '0') {
            $zip[0] = 'O';
        }
        if ($zip[2] == '0') {
            $zip[2] = 'O';
        }
        if ($zip[5] == '0') {
            $zip[5] = 'O';
        }
       //uppercase all the letters
        strtoupper($zip);
   }

The first tests I ran were of the sort:

input[0o0 O0o] => output[O0O 0O0]

Everything looks good I said to myself, it's working! But then I tried a normal postal code and keep getting unexpected results:

input[S7K3K1] => output[S0K 0K0]

I can't figure out why the code is deciding that ($zip[1] == ('O' || 'o') is true when $zip[1] == 7.

Any input would be greatly appreciated. Also, if you see a better way of normalizing this input, please share!

Answer 1

   //let's put their o's, O's and 0's in the right places
    if ($zip[1] == ("O" || "o")) {
        $zip[1] = '0';
    }

This code does not do what you think – your comparison logic are wrong, because so is your understanding of the || operator.

Use console.log(("O" || "o")) and see what you get in console – ooops, that’s just the letter O. Why? Because the || logical or operator in JS returns the first value that is not false-y.

You need to either write two individual comparisons here, and or-conjoin those – $zip[1] == "O" || $zip[1] == "o", or use an array with possible values and then check whether your variable value is among those (but the latter would be a bit over the top here).

Edit: Or, as bigmandan pointed out, you could also transform your letter to upper- or lower-case first, then you only have to do one comparison: ($zip[1]).toLowerCase() == "o" (Of course this works only in a special case like this – if it was not O or o, but a or b instead, you would still have to do individual comparisons.)