문자열 변환 채택완료

<?php
$replace = array(
            '0' => 'A',
            '1' => 'B',
            '2' => 'C',
            '3' => 'D',
            '4' => 'E',
            '5' => 'F',
            '6' => 'G',
            '7' => 'H',
            '8' => 'I',
            '9' => 'J',
            'A' => 'K',
            'B' => 'L',
            'C' => 'M',
            'D' => 'N',
            'E' => 'O',
            'F' => 'P',
            'G' => 'Q',
            'H' => 'R',
            'I' => 'S',
            'J' => 'T',
            'K' => 'U',
            'L' => 'V',
            'M' => 'W',
            'N' => 'X',
            'O' => 'Y',
            'P' => 'Z',
            'Q' => '0',
            'R' => '1',
            'S' => '2',
            'T' => '3',
            'U' => '4',
            'V' => '5',
            'W' => '6',
            'X' => '7',
            'Y' => '8',
            'Z' => '9'
           );

$str = 'test';

$len = strlen($str);

for($i=0; $i<$len; $i++) {
    $key = strtoupper($str[$i]);

    echo $replace[$key];
}
?>