Increment letters in PHP?

Question

Recently I needed to increment letters in PHP within a loop.

For each iteration, instead of numerical indexes, it needed letters of the alphabet.

So, as I already know that PHP does letter incrementing (and because it’s very simple), I did something similar to this.

for($letra = 'a'; $letra != 'aa'; $letra++) {

    echo $letra;
}

// abcdefghijklmnopqrstuvwxyz

However, because I have never seen it documented or in any other language I know a feature like this, I was in doubt whether I should use it or not.

Because of coding (and among others), it is safe to use this feature, or it is better to appeal to friends chr or the range('a', 'z'), as in the example below?

for($letra = 97; $letra <= 122; $letra++) {

    echo chr($letra);
}

//abcdefghijklmnopqrstuvwxyz


echo implode('', range('a', 'z')); //abcdefghijklmnopqrstuvwxyz

//abcdefghijklmnopqrstuvwxyz

Answer 1

This is typical of weakly typed language such as C for example. One type can be used as if it were another. Note that this is different from being dynamically typed, so much so that C is statically typed (and behaves somewhat differently).

At first there are no problems. It does not cause errors of any kind. It is only recommended to avoid this feature when it is possible because it is easy use wrong. Of course in simple situations like this it is difficult to make a mistake.

Whether it is possible to explicitly say what the intention is (working with characters) is a little better from a readability point of view. Those who do not know this feature may wonder the first code of the question. But to say that is wrong is preciousness.

I know it’s just an example but in this case I would even use is a string literal :)

Answer 2

As already mentioned, this is characteristic of weakly typed languages. this works because increment is done in the code ASCII(A-Z 65-90, a-z 97-122), and not exactly in the letter you see. This works only with increment operator(++). Already with the decreasing is not possible, IE, can not create a string z-a Z-A.

The manual speaks of this behavior, which he follows the convesion Perl which says that the valid set for the increment is (a-z, A-Z and 0-9), so z flipped aa, in C he would follow the next ASCII code.

This feature is useful when mounting the header of a worksheet where the coordinates are ex: A1, B1 ...

Examples in Perl

$char = 'z';
print ++$char; //saída: aa

Equivalent example of crease()

@alfabeto = ('a'..'z');

foreach(@alfabeto){
    print $_
}

Answer 3

It is normal to do this way, if I were to need a solution so I would do this way:

foreach (range('a', 'z') as $letra) {
   print $letra;
}