String Replacer

replace.php

<?php
if ($_GET['Proses'])
{
	$awal = $_GET["awal"];
	$Decrypter_variables = array(
		"1", "2", "3", "4", "5", "6", "7", "8", "9", 
		"%", "!", "@", "#", "$", "^", "&", "*", "~", 
		"+", ":", "-", "=", "?", "'", ".", "<" );
	$Variables_assign = array(
		"a", "b", "c", "d", "e", "f", "g", "h", "i", 
		"j", "k", "l", "m", "n", "o", "p", "q", "r", 
		"s", "t", "u", "v", "w", "x", "y", "z" );
	$Newer = str_replace($Decrypter_variables, $Variables_assign, $awal);
}
?>

<form action="" method="GET">
<table border="0" width="500">
<tr>
    <td><b>OUTPUT</b></td>
    <td>=</td>
    <td><input type="text" name="awal" value="<?php echo $awal; ?>"></td>
</tr>
<tr>
    <td colspan="3" align="center">
    	<input type="submit" value="Proses" name="Proses">
    </td>
</tr>
<tr>
    <td><b>HASIL</b></td>
    <td>=</td>
    <td><input type="text" name="akhir" value="<?php echo $Newer; ?>"></td>
</tr>
</table>
</form>