- array_combine: documentation ( source)
- implode: documentation ( source)
- strrev: documentation ( source)
- range: documentation ( source)
- str_split: documentation ( source)
<?php
$dni = '342501198701065';
$row = str_split(strrev($dni));
$letters = array_combine(range(0,25), range('a', 'z'));
//now just use:
foreach($row as $n){
$dni_a[] = $letters[$n];
}
$dni2 = implode($dni_a);
echo $dni2;