json_encode的实现方法

json_encode的实现方法

<?php  
function __json_encode( $data ) {             
    if( is_array($data) || is_object($data) ) {  
        $islist = is_array($data) && ( empty($data) || array_keys($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, "\\\"\n\r\t/" . 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 ) {  
                $json .= sprintf("\\u%04x", ($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;  
}  
?>