Php，undo mysql_real_escape_string

Question

I really have the reason to reserve this function. I used to saved BINARY content to file, which was run by this function, so the content is something like

WA\0,\0\0\0\0\0\0„Cźw\\\0\0\0\0\0\0\0\0\0\0\0Q\0\0\0

so somehow I must reverse this function. I tried the stripslashes() function, now it looks better:

WA ,      „Cźw\           Q   

still corrupt. I even tried this one:

$search = array( "\0", "
", "", "\\", "\'", "\\", "\Z" );
$replace = array( "\x00", "
", "", "\"", "'", "\", \x1a" );
$a = str_replace($search, $replace, $a);

still no joy. How to restore the original binary data?

Answer 1

The trick is in properly escaping the sequences you want to replace. The following function should work.

function un_mysql_real_escape_string( $data ) {
    return str_replace(
        array( '\0'  , '
', '', '\Z'  , '\"', '\\\'', '\\\\' ),
        array( "\x00", "
", "", "\x1a", '"' , '\''  , '\\'   ),
        $data
    );
}

Unit test for my unescape function.

$data = '';
foreach ( range(0, 255) as $dec ) {
    $data .= chr( $dec );
}

$data_escaped = mysql_real_escape_string( $data );
var_dump( un_mysql_real_escape_string( $data_escaped ) === $data );