PHP兼容低版本和高版本的json数据处理类

json数据格式是当下比较流行的一种, 比起xml来,json格式更易用简单. 同时,与javascript配合起来可以说是最佳的数据交换格式. 在php 5.2以上版本,已经支持json的解析了,但是在php 5.2一下就不被支持了. 下面这个类可以实现兼容json_encode函数, 在高版本上,使用自带函数解析,低版本使用自定义函数解析,相信这种功能对PHP开发者来说很实用.

/* 
* 来源: http://www.xuehuwang.com/ 
* 作者: 雪狐博客 
*/
    final class Json {  
    static public function encode($data) {  
        if (function_exists('json_encode')) {  
            return json_encode($data);  
        } else {  
            switch (gettype($data)) {  
                case 'boolean':  
                    return $data ? 'true' : 'false';  
                case 'integer':  
                case 'double':  
                    return $data;  
                case 'resource':  
                case 'string':  
                    return '"' . str_replace(array("\r", "\n", "<", ">", "&"), array('\r', '\n', '\x3c', '\x3e', '\x26'), addslashes($data)) . '"';  
                case 'array':  
                    if (empty($data) || array_keys($data) === range(0, sizeof($data) - 1)) {  
                        $output = array();  
      
                        foreach ($data as $value) {  
                            $output[] = Json::encode($value);  
                        }  
      
                        return '[ ' . implode(', ', $output) . ' ]';  
                    }  
                case 'object':  
                    $output = array();  
      
                    foreach ($data as $key => $value) {  
                        $output[] = Json::encode(strval($key)) . ': ' . Json::encode($value);  
                    }  
      
                    return '{ ' . implode(', ', $output) . ' }';  
                default:  
                    return 'null';  
            }  
        }  
    }  
      
    static public function decode($json, $assoc = FALSE) {  
        if (function_exists('json_decode')) {  
            return json_decode($json);  
        } else {  
            $match = '/".*?(?<!\\\\)"/';  
      
            $string = preg_replace($match, '', $json);  
            $string = preg_replace('/[,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t]/', '', $string);  
      
            if ($string != '') {  
                return NULL;  
            }  
      
            $s2m = array();  
            $m2s = array();  
      
            preg_match_all($match, $json, $m);  
      
            foreach ($m[0] as $s) {  
                $hash = '"' . md5($s) . '"';  
                $s2m[$s] = $hash;  
                $m2s[$hash] = str_replace('$', '\$', $s);  
            }  
      
            $json = strtr($json, $s2m);  
      
            $a = ($assoc) ? '' : '(object) ';  
      
            $data = array(  
                ':' => '=>',  
                '[' => 'array(',  
                '{' => "{$a}array(",  
                ']' => ')',  
                '}' => ')'
            );  
      
            $json = strtr($json, $data);  
      
            $json = preg_replace('~([\s\(,>])(-?)0~', '$1$2', $json);  
      
            $json = strtr($json, $m2s);  
      
            $function = @create_function('', "return {$json};");  
            $return = ($function) ? $function() : NULL;  
      
            unset($s2m);  
            unset($m2s);  
            unset($function);  
      
            return $return;  
        }  
    }  
}