How to increment letters like numbers in PHP ?

Given some letters and the task is to increment letters like we increment numbers. We will encounter various cases and establish a result.

Example:

• Numbers after increment

  0 1 2 3...

• Letters after increment

  a b c d...

One more interesting thing to notice is that just like numbers start with double-digit after 9 letters do the same after encountering ‘z’

• Numbers:

  0 1 2 3 ... 9 10 11 12 .. . 99 100 101 ...

• Letters:

  a b c d ... z aa ab ac ... zz aaa aab ...

This can be carried out using the simple increment (++) operator just like in numbers. The only point of difference being decrement (–) operator doesn’t work the same in letters as it does in numbers.

Example 1: Program to increment various letters and print it.

<?php
$i = 'a';
print(++$i . " ");

$j = 'aa';
print(++$j . " ");

$k = 'aaa';
print(++$k . " ");

$l = 'aaaa';
print(++$l);
?>

Output:

b ab aab aaab

Example 2: Program to print all letters between ‘a’ to ‘y’.

<?php
$i = 'a';

for( $i; $i < 'z'; $i++ )
    print($i);
?>

Output: This example is looped till ‘y’ because if the limit in for is set until it reaches ‘z’, the required result is different. The loop executes until it encounters ‘z’

abcdefghijklmnopqrstuvwxy

Note: Decrement doesn’t work on letters

Program 3: Program to show that decrement doesn’t work on letters.

<?php
$i = 'd';

for( $i; $i > 'a'; $i-- )
    print($i);
?>

Output:

The following program produces an infinite loop of letter 'd'