var_dump()

(PHP 4, PHP 5, PHP 7)

打印变量的相关信息

说明

此函数显示关于一个或多个表达式的结构信息，包括表达式的类型与值。数组将递归展开值，通过缩进显示其结构。

In PHP 5 all public, private and protected properties of objects will be returned in the output.

和直接将结果输出到浏览器一样，可使用输出控制函数来捕获当前函数的输出，然后(例如)保存到一个string中。

参数

你要打印的变量。

返回值

没有返回值。

范例

Example #1var_dump()例子

以上例程会输出：

array(3) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  array(3) {
    [0]=>
    string(1) "a"
    [1]=>
    string(1) "b"
    [2]=>
    string(1) "c"
  }
}

以上例程会输出：

float(3.1)
bool(true)

参见

• var_export() 输出或返回一个变量的字符串表示
• print_r() 以易于理解的格式打印变量。

Keep in mind if you have xdebug installed it will limit the var_dump() output of array elements and object properties to 3 levels deep.
To change the default, edit your xdebug.ini file and add the folllowing line:
xdebug.var_display_max_depth=n
More information here:
http://www.xdebug.org/docs/display

If you're like me and uses var_dump whenever you're debugging, you might find these two "wrapper" functions helpful.
This one automatically adds the PRE tags around the var_dump output so you get nice formatted arrays.

This one returns the value of var_dump instead of outputting it.

Fairly simple functions, but they're infinitely helpful (I use var_dump_pre() almost exclusively now).

I post a new var_dump function with colors and collapse features. It can also adapt to terminal output if you execute it from there. No need to wrap it in a pre tag to get it to work in browsers. 

You can pass arguments like this:

Hope it works well for you!

a html-encoded var_dump

(creds: ekneuss / mOo @ irc.freenode.net/#php )

If you want to save exactly the content of an array into a variable to save ir later for example, use this:

You'll have in your same variable the content readable, instead of written down or anything else

Be careful this outputs to stdout stream (1) instead of the proper stderr stream (2).

You can also use the PEAR package available at http://pear.php.net/package/Var_Dump
which parses the variable content in a very pleasant manner, a lot more easier to "follow" than the built-in var_dump() function. 
Of course there are many others, but I prefer this one, because it's simply to use.
Just add at the begining of your file:

then, instead of simply using var_dump($foo), use:

Read the documentation if you're looking for different output layouts.
Cheers!
Vladimir Ghetau

dumping objects that reference each other could lead to infinite recursion 

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