How to make a simple cipher?

Question

PHP

For example, A = 1, B = 2, C = 3;
If you write in the AB text field, then 12 is displayed, and if CB, then 32, etc.?

Answer 1

Use str_replace:

$a = ['A', 'B', 'C'];
$b = ['1', '2', '3'];
echo str_replace($a, $b, 'CB');