javascript 如何在警报消息框中显示 print_r() 内容？

How to show print_r() content in alert message box?

提问by Brian

I know that whenever I write

我知道每当我写

$food = array('fruit'=>'apple', 'veggie'=>'tomato', 'bread'=>'wheat');
$text = print_r($food, true);
echo $text;

Output will be:

输出将是：

Array('fruit'=>'apple', 'veggie'=>'tomato', 'bread'=>'wheat')

Array('水果'=>'苹果','蔬菜'=>'番茄','面包'=>'小麦')

But when I am trying to display this via alert message box, it does not show anything.
The code for js alert I wrote as follows:

但是当我尝试通过警报消息框显示它时，它没有显示任何内容。
我写的js alert的代码如下：

echo "<script type='text/javascript'> alert('{$text}') </script>"; 

This does not work. When I assign a different string to $text then it works. Seems like alert() does not like the format of $test string. If I write in this way:

这不起作用。当我为 $text 分配一个不同的字符串时，它就起作用了。似乎 alert() 不喜欢 $t​​est 字符串的格式。如果我这样写：

echo "<script type='text/javascript'> alert('Array('fruit'=>'apple', 'veggie'=>'tomato', 'bread'=>'wheat')') </script>";

I get the correct output. So not sure what is wrong there.

我得到正确的输出。所以不确定那里有什么问题。

回答by Danijel

To convert PHP array into javascript array you must use json_encode. JSON (JavaScript Object Notation) is a format for data-interchange between programming languages based on the JavaScript. Because JSON is a text format, the result of encoding can be used as a string or as a javascript object.

要将 PHP 数组转换为 javascript 数组，您必须使用json_encode。JSON（JavaScript Object Notation）是一种基于 JavaScript 的编程语言之间数据交换的格式。因为 JSON 是一种文本格式，所以编码的结果可以用作字符串或 javascript 对象。

$food = array('fruit'=>'apple', 'veggie'=>'tomato', 'bread'=>'wheat');

// show the array as string representation of javascript object
echo "<script type='text/javascript'> alert('".json_encode($food)."') </script>";

// show the array as javascript object
echo "<script type='text/javascript'> alert(".json_encode($food).") </script>";

// show the output of print_r function as a string
$text = print_r($food, true);
echo "<script type='text/javascript'> alert(".json_encode($text).") </script>";

A few tips for debugging:

调试的一些技巧：

• for inspection of JavaScript objects, console.logis a very useful

• if you want a cleaner print_routput ( on Windows) use:

  function print_r2($val){
      echo '<pre>'.print_r($val, true).'</pre>';
  }
  

• 对于 JavaScript 对象的检查，console.log是一个非常有用的

• 如果您想要更清晰的print_r输出（在 Windows 上），请使用：

  function print_r2($val){
      echo '<pre>'.print_r($val, true).'</pre>';
  }