php实现json_encode的代码实例

<?php 
/**
 * php json_encode代码
 * site http://www.jb200.com
*/
    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, ""nrt/" . 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%04xu%04x", $w1, $w2); 
                } 
            } 
        } else { 
            # int, floats, bools, null 
            $json = strtolower(var_export( $data, true )); 
        } 
        return $json; 
    } 
?>