如何在php中创建一个空白的关联数组

问题描述：

My php script returns data to the web client where it is processed by javaScript.

If data is found it is stored in an associative array / object. If no data is found I would like to send a blank associative array.

The only example I have seen on line is in the manual where you create an empty class and then instantiate an object from that.

Below is my code and the results it produces on the web client side

            $sql = 'select job, client, project from jobs j left join client c on c.key = j.cKey where j.key='.$this->p['reckey'];
        if ( $result = $db->query($sql) )
        {
            if ($result->num_rows > 0)
            {
                $l = mysqli_fetch_all( $result, $resulttype = MYSQLI_ASSOC );
                $this->res_array['info'] = $l[0];
            }else{
                $this->errors[] = 'No such job # '.$this->p['reckey'];
                $this->res_array['info']=[];
            }
        }else{
            $this->errors[] = 'Query failed!';
            $this->res_array['info']=[];
        }
        $this->res_array['errors'] = $this->errors;
        echo json_encode ($this->res_array);

Here are two examples of what the data looks like when it arrives at the web client before it is decoded by JSON. Note the difference in the "info" element.

response {"info":{"job":"999","client":"My Company, Inc. ","project":"This Project"},"errors":[]}

error response {"info":[ ],"errors":["No such job # 0"]}

In the successful response I have an object/associative array where I would use the

for (variable in object) {...}

In the blank response I just get the standard array [ ] square brackets where I would use the

for (step = 0; step < info.length; step++) {}

This occurs of course because I am specifying a blank array in the php code above.

My question is simple how can I change my php code so a blank associtive array is transmitted?

我的php脚本将数据返回到由JavaScript处理的Web客户端。 p>

如果找到数据，则将其存储在关联数组/对象中。如果没有找到数据，我想发送一个空白的关联数组。 p>

我在线看到的唯一例子是在手册中你创建一个空类，然后从中实例化一个对象下面是我的代码及其在Web客户端生成的结果 p>

  $ sql ='select job，client， 来自作业的项目j在c.key = j.cKey上离开加入客户端c其中j.key ='。$ this-＆gt; p ['reckey']; 
 if（$ result = $ db-＆gt; query（$  sql））
 {
 if if（$ result-＆gt; num_rows＆gt; 0）
 {
 $ l = mysqli_fetch_all（$ result，$ resulttype = MYSQLI_ASSOC）; 
 $ this-＆gt; res_array ['info  '] = $ l [0]; 
}其他{
 $ this-＆gt; errors [] ='没有这样的工作＃'。$ this-＆gt; p ['reckey']; 
 $ this-＆gt  ; res_array ['info'] = []; 
} 
}其他{
 $ this-＆gt; errors [] ='查询失败！'; 
 $ this-＆gt; res_array ['info'] =  []; 
} 
 $ this-＆gt; res_array  ['errors'] = $ this-＆gt; errors; 
 echo json_encode（$ this-＆gt; res_array）; 
  code>  pre> 
 
 以下是两个例子 数据在它被JSON解码之前到达Web客户端时看起来像。 请注意“info”元素的区别。 p> 
 
 
响应{“info”：{“job”：“999”，“client”：“My Company，Inc。”  ，“项目”：“此项目”}  strong>，“错误”：[]}  p> 
 
 
错误回复{“信息”：[]  strong>，  “错误”：[“没有这样的作业＃0”]}  p> 
 
 
在成功的响应中，我有一个对象/关联数组，我将使用 p> 
 
   for（对象中的变量）{...} 
  code>  pre> 
 
 
在空白响应中我只得到标准数组[]方括号 使用 p> 
 
 

  for（step = 0; step＆lt; info.length; step ++）{} 
  code>  pre> 
 
  这当然是因为我在上面的php代码中指定了一个空白数组。   p> 
 
 
我的问题很简单，如何更改我的PHP代码，以便传输空白的关联数组？ p> 
  div>

答

The only example I have seen on line is in the manual where you create an empty class and then instantiate an object from that.

Sounds like you've answered your own question!

Since in JavaScript an object and an associative array are basically the same thing all you have to do is replace this line:

$this->res_array['info']=[];

With this one:

$this->res_array["info"] = new StdClass;

Or if you want to make the change only before sending the response you could check for an empty info array and replace it with an empty class.

if(!count($this->res_array["info"]))
    $this->res_array["info"] = new StdClass;

答

I would suggest to take the best of both worlds, and let PHP generate an array of associative arrays, even though you expect at the most one, but at least you'd use the same structure for when you have none.

So change:

$this->res_array['info'] = $l[0];

to:

$this->res_array['info'] = $l;

And then in JavaScript do:

for (var step = 0; step < info.length; step++) {
    for (variable in info[step]) {
        // ...
    }
}

... and if you still need to, you can deal with the no-data condition separately in JavaScript. Something like:

if (errors.length) {
    // deal with this case...
}

如何在php中创建一个空白的关联数组

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