var_export

(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)

var_export — 输出或返回变量的可解析字符串表示

说明

var_export(mixed $value, bool $return = false): ?string

var_export() 函数返回关于传递给该函数的变量的结构信息，它和 var_dump() 函数类似，不同的是其返回的表示是合法的 PHP 代码。

参数

value: 想要输出的变量名。
return: 此参数为 true 时，var_export() 将返回一个变量，而不是输出它。

返回值

参数 return 为 true 时返回变量。否则返回 null。

更新日志

版本	说明
8.2.0	现在导出的是完整类名；以前会省略开头反斜线。
7.3.0	现在将 stdClass 对象作为数组类型转换为对象输出（ `(object) array( ... )`），而不是使用不存在的 stdClass::__setState() 方法。实际效果是，现在 stdClass 是可输出的，生成的代码甚至可以在早期的 PHP 版本上运行。

示例

示例 #1 var_export() 示例

<?php
$a = array (1, 2, array ("a", "b", "c"));
var_export($a);
?>

以上示例会输出：

array (
  0 => 1,
  1 => 2,
  2 => 
  array (
    0 => 'a',
    1 => 'b',
    2 => 'c',
  ),
)

<?php

$b = 3.1;
$v = var_export($b, true);
echo $v;

?>

以上示例会输出：

3.1

示例 #2 输出 stdClass 类 (自 PHP 7.3.0 起)

<?php
$person = new stdClass;
$person->name = 'ElePHPant ElePHPantsdotter';
$person->website = 'https://php.net/elephpant.php';

var_export($person);

以上示例会输出：

(object) array(
   'name' => 'ElePHPant ElePHPantsdotter',
   'website' => 'https://php.net/elephpant.php',
)

示例 #3 输出对象 (自 PHP 5.1.0 起)

<?php
class A { public $var; }
$a = new A;
$a->var = 5;
var_export($a);
?>

以上示例会输出：

A::__set_state(array(
   'var' => 5,
))

示例 #4 使用 __set_state()

<?php
class A
{
    public $var1;
    public $var2;

    public static function __set_state($an_array)
    {
        $obj = new A;
        $obj->var1 = $an_array['var1'];
        $obj->var2 = $an_array['var2'];
        return $obj;
    }
}

$a = new A;
$a->var1 = 5;
$a->var2 = 'foo';

eval('$b = ' . var_export($a, true) . ';'); // $b = A::__set_state(array(
                                            //    'var1' => 5,
                                            //    'var2' => 'foo',
                                            // ));
var_dump($b);
?>

以上示例会输出：

object(A)#2 (2) {
  ["var1"]=>
  int(5)
  ["var2"]=>
  string(3) "foo"
}

注释

注意:
类型为 resource 的变量无法通过此函数输出。

注意:
var_export() 不处理循环引用，因为几乎不可能为此生成可解析的 PHP 代码。如果您想对数组或对象的完整表示进行操作，请使用 serialize()。

警告

PHP 8.2.0 之前，当 var_export() 输出对象时，为了最大的兼容性，命名空间类的类名中不包含前导反斜杠。

注意:
为了能够执行 var_export() 生成的 PHP ，所有被处理的对象必须实现 __set_state 魔术方法。唯一的例外是 stdClass ，它作为数组类型转换为对象输出。

参见

print_r() - 打印人类可读的变量信息
serialize() - 生成值的可存储表示
var_dump() - 打印变量的相关信息

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＋添加备注

用户贡献的备注 21 notes

down

steven at nevvix dot com ¶

5 years ago

I improved my previous varexport().

<?php
/**
 * PHP var_export() with short array syntax (square brackets) indented 2 spaces.
 *
 * NOTE: The only issue is when a string value has `=>\n[`, it will get converted to `=> [`
 * @link https://www.php.net/manual/en/function.var-export.php
 */
function varexport($expression, $return=FALSE) {
    $export = var_export($expression, TRUE);
    $patterns = [
        "/array \(/" => '[',
        "/^([ ]*)\)(,?)$/m" => '$1]$2',
        "/=>[ ]?\n[ ]+\[/" => '=> [',
        "/([ ]*)(\'[^\']+\') => ([\[\'])/" => '$1$2 => $3',
    ];
    $export = preg_replace(array_keys($patterns), array_values($patterns), $export);
    if ((bool)$return) return $export; else echo $export;
}

$array = [
    'str' => 'Test
       spaces',
       0 => 33,
       1 => TRUE,
       [3,4,'d',[]],
    'arr' => [
        'text with spaces' => '[Tes\'t"s":
 => [
 => 
  [
   {
      spaces',
    ],
    "str2" => "Test's'
 } spaces",
    'arr2' => [
        'text with spaces' => [
            'arr3' => [
                'text with spaces' => 'Te": "st \' => [
      spaces',
            ],
        ],
    ],
];
varexport($array);
// Result:
```
[
  'str' => 'Test
       spaces',
  0 => 33,
  1 => true,
  2 => [
    0 => 3,
    1 => 4,
    2 => 'd',
    3 => [
    ],
  ],
  'arr' => [
    'text with spaces' => '[Tes\'t"s":
 => [
 => [
   {
      spaces',
  ],
  'str2' => 'Test\'s\'
 } spaces',
  'arr2' => [
    'text with spaces' => [
      'arr3' => [
        'text with spaces' => 'Te": "st \' => [
      spaces',
      ],
    ],
  ],
]
```
NOTE: The only issue is when a string value has `=>\n[`, it will get converted to `=> [`

down

steven at nevvix dot com ¶

6 years ago

/**
 * var_export() with square brackets and indented 4 spaces.
 */
<?php
function varexport($expression, $return=FALSE) {
    $export = var_export($expression, TRUE);
    $export = preg_replace("/^([ ]*)(.*)/m", '$1$1$2', $export);
    $array = preg_split("/\r\n|\n|\r/", $export);
    $array = preg_replace(["/\s*array\s\($/", "/\)(,)?$/", "/\s=>\s$/"], [NULL, ']$1', ' => ['], $array);
    $export = join(PHP_EOL, array_filter(["["] + $array));
    if ((bool)$return) return $export; else echo $export;
}

down

Mark P ¶

8 years ago

It doesn't appear to be documented, but the behaviour of `var_export()` changed in PHP 7.

Previously, `var_export(3.)` returned "3", now it returns "3.0".

down

chudinov at yahoo dot com ¶

11 years ago

Looks like since version 5.4.22 var_export uses the serialize_precision ini setting, rather than the precision one used for normal output of floating-point numbers.
As a consequence since version 5.4.22 for example var_export(1.1) will output 1.1000000000000001 (17 is default precision value) and not 1.1 as before. 

<?php 
//ouput 1.1000000000000001
var_export(1.1)
 ?>

down

4n4jmza02 at sneakemail dot com ¶

14 years ago

I learned the hard way that if var_export encounters a resource handle it exports it as "NULL", even if it is a valid handle. The documentation states that a handle cannot be exported, but it does not describe what happens if you try to do so anyway.

I had been using var_export in some debugging code while tracing a problem with a resource handle not being generated and ended up thinking that null handles were still being generated long after the problem had been fixed.

down

dan at coders dot co dot nz ¶

10 years ago

I found that my complex type was exporting with 
  stdClass::__set_state()
in places. Not only was that strange and messy, it cannot be eval()-ed back in at all. Fatal error. Doh!

However a quick string-replace tidy-up of the result rendered it valid again.

    $macro = var_export($data, TRUE);
    $macro = str_replace("stdClass::__set_state", "(object)", $macro);
    $macro = '$data = ' . $macro . ';';

And now the string I output *can* be evaluated back in again.

down

laszlo dot heredy at gmail dot com ¶

14 years ago

Try this function instead of var_export($GLOBALS) or var_dump($GLOBALS) when all you want to know is the values of the variables you set on the current page.



<?php

function globalvars(){

    $result=array();

    $skip=array('GLOBALS','_ENV','HTTP_ENV_VARS',

                        '_POST','HTTP_POST_VARS','_GET',

                        'HTTP_GET_VARS',

                        '_COOKIE',

                        'HTTP_COOKIE_VARS','_SERVER',

                        'HTTP_SERVER_VARS',

                        '_FILES','HTTP_POST_FILES',

                        '_REQUEST','HTTP_SESSION_VARS',

                        '_SESSION');

    foreach($GLOBALS as $k=>$v)

        if(!in_array($k,$skip))

            $result[$k]=$v;

    return $result;

}//functionglobalvars



var_export(globalvars());

?>

down

linus at flowingcreativity dot net ¶

19 years ago

<roman at DIESPAM dot feather dot org dot ru>, your function has inefficiencies and problems. I probably speak for everyone when I ask you to test code before you add to the manual.

Since the issue of whitespace only comes up when exporting arrays, you can use the original var_export() for all other variable types. This function does the job, and, from the outside, works the same as var_export().

<?php

function var_export_min($var, $return = false) {
    if (is_array($var)) {
        $toImplode = array();
        foreach ($var as $key => $value) {
            $toImplode[] = var_export($key, true).'=>'.var_export_min($value, true);
        }
        $code = 'array('.implode(',', $toImplode).')';
        if ($return) return $code;
        else echo $code;
    } else {
        return var_export($var, $return);
    }
}

?>

down

NitPicker ¶

11 years ago

When it comes to HTML output (as discussed below), it's all fun and games until someone pokes their eye out with a "<".

Surround it with "<pre>", but do remember to wrap it in htmlspecialchars() as well.

down

beverasrilakshmi at gmail dot com ¶

5 years ago

Just for fun, trying to understand the definition of "returns parsable string"....any type of variable passed to var_export, the return value will be a typecasted as string...

<?php 

$var = 1;
var_dump($var); //type is int as expected 
echo "<br>";
$var_after_export = var_export($var,true); //returning $var will now makes it a string
var_dump($var_after_export);

?>

down

john dot risken at gmail dot com ¶

14 years ago

I didn't see this simple little item anywhere in the user notes. Maybe I'm blind!



Anyway, var_export and print_r both use spaces and carriage returns for formatting.  Sent to an html page, most of the formatting is lost. This simple function prints a nicely formatted array to an html screen:



<?php

function pretty_var($myArray){

    print str_replace(array("\n"," "),array("<br>","&nbsp;"), var_export($myArray,true))."<br>";

}

?>

down

Glen ¶

17 years ago

Like previously reported, i find var_export() frustrating when dealing with recursive structures.  Doing a :

<?php
var_export($GLOBALS);
?>

fails.  Interestingly, var_dump() has some logic to avoid recursive references.  So :

<?php
var_dump($GLOBALS);
?>

works (while being more ugly).  Unlike var_export(), var_dump() has no option to return the string, so output buffering logic is required if you want to direct the output.

down

ravenswd at gmail dot com ¶

15 years ago

(This replaces my note of 3-July-2009. The original version produced no output if a variable contained an empty array, or an array consisting only of empty arrays. For example, $bigarray['x'] = array(); Also, I have added a second version of the function.)

The output can be difficult to decipher when looking at an array with many levels and many elements on each level. For example:

<?php
print ('$bigarray = ' . var_export($bigarray, true) . "\n");
?>

will return:

$bigarray = array(
... (500 lines skipped) ...
          'mod' => 'charlie',

Whereas the routine below can be called with:

<?php
recursive_print ('$bigarray', $bigarray);
?>

and it will return:

$bigarray = array()
... (500 lines skipped) ...
$bigarray['foo']['bar']['0']['somethingelse']['mod'] = 'charlie'

Here's the function:

<?php
function recursive_print ($varname, $varval) {
  if (! is_array($varval)):
    print $varname . ' = ' . $varval . "<br>\n";
  else:
    print $varname . " = array()<br>\n";
    foreach ($varval as $key => $val):
      recursive_print ($varname . "['" . $key . "']", $val);
    endforeach;
  endif;
}
?>

For those who want a version that produces valid PHP code, use this version:

<?php
function recursive_print ($varname, $varval) {
  if (! is_array($varval)):
    print $varname . ' = ' . var_export($varval, true) . ";<br>\n";
  else:
    print $varname . " = array();<br>\n";
    foreach ($varval as $key => $val):
      recursive_print ($varname . "[" . var_export($key, true) . "]", $val);
    endforeach;
  endif;
}
?>

If your output is to a text file and not an HTML page, remove the <br>s.

down

sergei dot solomonov at gmail dot com ¶

12 years ago

<?php

$closure = function(){};



var_export($closure);



// output: Closure::__set_state(array())

?>

down

jodybrabec at gmail dot com ¶

12 years ago

WORKAROUND for error "Nesting level too deep - recursive dependency":
ob_start();
var_dump($GLOBALS);
$dataDump = ob_get_clean();
echo $dataDump;

down

Anonymous ¶

13 years ago

There is an even simpler way to have clean output from var_export and print_r in html pages:

<?php 
function pretty_var($myArray)
{ 
    echo "<pre>";
    var_export($myArray);
    echo "</pre>";
} 
?>

down

stangelanda at arrowquick dot com ¶

17 years ago

I have been looking for the best method to store data in cache files.

First, I've identified two limitations of var_export verus serialize.  It can't store internal references inside of an array and it can't store a nested object or an array containing objects before PHP 5.1.0.

However, I could deal with both of those so I created a benchmark.  I used a single array containing from 10 to 150 indexes.  I've generate the elements' values randomly using booleans, nulls, integers, floats, and some nested arrays (the nested arrays are smaller averaging 5 elements but created similarly).  The largest percentage of elements are short strings around 10-15 characters.  While there is a small number of long strings (around 500 characters).

Benchmarking returned these results for 1000 * [total time] / [iterations (4000 in this case)]

serialize 3.656, 3.575, 3.68, 3.933, mean of 3.71
include 7.099, 5.42, 5.185, 6.076, mean of 5.95
eval 5.514, 5.204, 5.011, 5.788, mean of 5.38

Meaning serialize is around 1 and a half times faster than var_export for a single large array.  include and eval were consistently very close but eval was usually a few tenths faster (eval did better this particular set of trials than usual). An opcode cache like APC might make include faster, but otherwise serialize is the best choice.

down

paul at worldwithoutwalls dot co dot uk ¶

20 years ago

var_export() differs from print_r() for variables that are resources, with print_r() being more useful if you are using the function for debugging purposes.
e.g.
<?php
$res = mysql_connect($dbhost, $dbuser, $dbpass);
print_r($res); //output: Resource id #14
var_export($res); //output: NULL
?>

down

me at peterkooi dot com ¶

1 month ago

A small function for exporting variables as string, supporting nested arrays, with indented output, blockquoted and with double quotes, that can be pasted back in code.

<?php
function dump($value) {
  function _dump($value, $indent = 0) {
    if (!is_array($value)) return json_encode($value, JSON_NUMERIC_CHECK);
    foreach($value as $key => $item) $result .= (ifset($result) ? ",\r\n" . str_repeat(" ", $indent + 2) : "") . json_encode($key) . " => " . _dump($item, $indent + 2);
    return "[\r\n" . str_repeat(" ", $indent + 2) . "$result\r\n" . str_repeat(" ", $indent) . "]";
  }
  return "<pre>" . htmlspecialchars(_dump($value)) . "</pre>";
}

down

php_manual_note at bigredspark dot com ¶

21 years ago

[john holmes]

True, but that method would require you to open and read the file into a variable and then unserialize it into another variable.



Using a file created with var_export() could simply be include()'d, which will be less code and faster. 



[kaja]

If you are trying to find a way to temporarily save variables into some other file, check out serialize() and unserialize() instead - this one is more useful for its readable property, very handy while debugging.



[original post]

If you're like me, you're wondering why a function that outputs "correct PHP syntax" is useful. This function can be useful in implementing a cache system. You can var_export() the array into a variable and write it into a file. Writing a string such as



<?php

$string = '<?php $array = ' . $data . '; ?>';

?>



where $data is the output of var_export() can create a file that can be easily include()d back into the script to recreate $array. 



The raw output of var_export() could also be eval()d to recreate the array.



---John Holmes...

down

rarioj at gmail dot com ¶

15 years ago

NOTE: If an object Foo has __set_state() method, but if that object contains another object Bar with no __set_state() method implemented, the resulting PHP expression will not be eval()-able.

This is an example (object Test that contains an instance of Exception).

<?php

class Test
{
  public $one;
  public $two;
  public function __construct($one, $two)
  {
    $this->one = $one;
    $this->two = $two;
  }
  public static function __set_state(array $array)
  {
    return new self($array['one'], $array['two']);
  }
}

$test = new Test('one', new Exception('test'));

$string = var_export($test, true);

/* $string =
Test::__set_state(array(
   'one' => 'one',
   'two' => 
  Exception::__set_state(array(
     'message' => 'test',
     'string' => '',
     'code' => 0,
     'file' => 'E:\\xampp\\htdocs\\test.Q.php',
     'line' => 35,
     'trace' => 
    array (
    ),
     'previous' => NULL,
  )),
))
*/

eval('$test2 = '.$string.';'); // Fatal error: Call to undefined method Exception::__set_state

?>

So avoid using var_export() on a complex array/object that contains other objects. Instead, use serialize() and unserialize() functions.

<?php

$string = 'unserialize('.var_export(serialize($test), true).')';

eval('$test2 = '.$string.';');

var_dump($test == $test2); // bool(true)

?>