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6 years ago
A nice, simple way of using rot-n. Allows for a lot of easy customisation, and works quickly. This function uses ASCII characters and values.

<?php

function rotn($val, $n) {
    $min = 0;
    $max = 127;
    $final = '';
    $new_string = str_split($val);
    
    foreach ($new_string as $letter) {
        $current = ord($letter);
        $val = $current+$n;

        if ($val >= $max) {
            $val = $val - $max;
        }

        if ($val <= $min) {
            $val = $val + $min;
        }

        $current = $val;
        $final .= chr($current);
    }

    return $final;
}

echo 'Test 123 (4) -> '.rotn("Test 123", 4).'<br>'; // Xiwx$567
echo 'Test 123 (8) -> '.rotn("Test 123", 8).'<br>'; // \m{|(9:;
echo 'Test 123 (-4) -> '.rotn("Test 123", -4).'<br>'; // Paop-./

$value = rotn("Test 123", 8);
echo 'Test 123 (Reverse [8 then -8]) -> '.rotn($value, -8).'<br>'; // Test 123

?>
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