[php] How to increment a letter N times per iteration and store in an array?

$letter = array();
for ($i = 'A'; $i !== 'ZZ'; $i++){
        $letter[] .= $i;
}
print_r($letter);

From above script I do a loop from A, B, C, D ... ZZ.

Now, I want to make it as A, C, E, G, I ... ZZ. (2 steps instead of 1)

I need direction to do it.

Here is your solution for the problem,

$letter = array();
for ($i = 'A'; $i !== 'ZZ'; $i++){
        if(ord($i) % 2 != 0)
           $letter[] .= $i;
}
print_r($letter);

You need to get the ASCII value for that character which will solve your problem.

Here is ord doc and working code.

For your requirement, you can do like this,

for ($i = 'A'; $i !== 'ZZ'; ord($i)+$x){
  $letter[] .= $i;
}
print_r($letter);

Here set $x as per your requirement.