Escaping escape Characters

Question

I\'m trying to mimic the json_encode bitmask flags implemented in PHP 5.3.0, here is the string I have:

$s = addslashes(\'O\\\'Rei\"lly\'); // O         


        

Answer 1

When you encode a string for json, some things have to be escaped regardless of the options. As others have pointed out, that includes '\' so any backslash run through json_encode will be doubled. Since you are first running your string through addslashes, which also adds backslashes to quotes, you are adding a lot of extra backslashes. The following function will emulate how json_encode would encode a string. If the string has already had backslashes added, they will be doubled.

function json_encode_string( $encode , $options ) {
    $escape = '\\\0..\37';
    $needle = array();
    $replace = array();

    if ( $options & JSON_HEX_APOS ) {
        $needle[] = "'";
        $replace[] = '\u0027';
    } else {
        $escape .= "'";
    }

    if ( $options & JSON_HEX_QUOT ) {
        $needle[] = '"';
        $replace[] = '\u0022';
    } else {
        $escape .= '"';
    }

    if ( $options & JSON_HEX_AMP ) {
        $needle[] = '&';
        $replace[] = '\u0026';
    }

    if ( $options & JSON_HEX_TAG ) {
        $needle[] = '<';
        $needle[] = '>';
        $replace[] = '\u003C';
        $replace[] = '\u003E';
    }

    $encode = addcslashes( $encode , $escape );
    $encode = str_replace( $needle , $replace , $encode );

    return $encode;
}