[SOLVED] Increment a character by more than 1 step

Increment a character by more than 1 step

Incrementing a character in php relative to its alphabetic position works as per:

$a = 'a'; 
++$a;
echo $a;

The output is 'b'

However, is it possible to increment the position by multiples? i.e. 10 for example.

$a = 'a'; 
$a += 2;
echo $a;

This outputs an integer, not 'c'.

Solution

You can convert the character into its ASCII value using ord(), increment/decrement that value then convert it back to a character using chr():

$a = 'a';
$num = 2;
$a = chr(ord($a)+$num);
echo $a;
// outputs c

ord- Return ASCII value of character
chr- Return a specific character

If you want the increment/decrement to wrap around a value that exceeds z then you can use this:

$a = 'a';
$num = 28;
echo chr((26 + (ord($a)+$num-97)) % 26 + 97);
// outputs c

Note: As php modulus of a negative number returns a negative number this will not work or $num values < -26 alternative solution include using gmp_mod as mentioned here.

Hope this helps!