This is a demonstration of a simple two way encryption in PHP. Keep in mind all (or most) encryption can be broke, so this is by no means expected to be "ultra" secure

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function encrypt_input($value)
{
	//first we want to loop through each character
    for($i = 0; $i < strlen($value); $i++ )
    {
    	//get the ascii value of each character and
    	//add 4 to it
    	$ascii_value[] = ord($value[$i]) + 4;
    }
    //return the encrypted value
    //each value is delimited with a ";"
    return implode(';', $ascii_value);
}
 
function decrypt_output($value)
{
	//first break the value into an array
	//split on our delimiter of ";"
    $value = explode(";", $value);
    
    //now loop through each item in the array
    for( $i = 0; $i < count($value); $i++ )
    {
    	//now we want the value of this item, then subtract
    	//4 from it (as we added 4 when encrypting)
        $value[$i] = chr($value[$i] - 4);
    }
    
    //now return the decrypted value
    return implode('', $value);
}