php实现json

<?PHP   

function __json_encode( $data ) {              

    if( is_array($data) || is_object($data) ) {   

        $islist = is_array($data) && ( emptyempty($data) || array_keys($data) === range(0,count($data)-1) );   

    

        if( $islist ) {   

            $json = '[‘ . implode(‘,’, array_map(‘__json_encode’, $data) ) . ‘]';   

        } else {   

            $items = Array();   

            foreach( $data as $key => $value ) {   

                $items[] = __json_encode("$key") . ':' . __json_encode($value);   

            }   

            $json = '{' . implode(',', $items) . '}';   

        }   

    } elseif( is_string($data) ) {   

        # Escape non-printable or Non-ASCII characters.   

        # I also put the \ character first, as suggested in comments on the 'addclashes' page.   

        $string = '"' . addcslashes($data, "\"

	/" . chr(8) . chr(12)) . '"';   

        $json    = '';   

        $len    = strlen($string);   

        # Convert UTF-8 to Hexadecimal Codepoints.   

        for( $i = 0; $i < $len; $i++ ) {   

    

            $char = $string[$i];   

            $c1 = ord($char);   

    

            # Single byte;   

            if( $c1 <128 ) {   

                $json .= ($c1 > 31) ? $char : sprintf("\u%04x", $c1);   

                continue;   

            }   

    

            # Double byte   

            $c2 = ord($string[++$i]);   

            if ( ($c1 & 32) === 0 ) {   
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                $json .= sprintf("\u%04x", ($c1 – 192) * 64 + $c2 – 128);   

                continue;   

            }   

    

            # Triple   

            $c3 = ord($string[++$i]);   

            if( ($c1 & 16) === 0 ) {   

                $json .= sprintf("\u%04x", (($c1 – 224) <<12) + (($c2 – 128) << 6) + ($c3 – 128));   

                continue;   

            }   

    

            # Quadruple   

            $c4 = ord($string[++$i]);   

            if( ($c1 & 8 ) === 0 ) {   

                $u = (($c1 & 15) << 2) + (($c2>>4) & 3) – 1;   

    

                $w1 = (54<<10) + ($u<<6) + (($c2 & 15) << 2) + (($c3>>4) & 3);   

                $w2 = (55<<10) + (($c3 & 15)<<6) + ($c4-128);   

                $json .= sprintf("\u%04x\u%04x", $w1, $w2);   

            }   

        }   

    } else {   

        # int, floats, bools, null   

        $json = strtolower(var_export( $data, true ));   

    }   

    return $json;   

}   

?>