var_export

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

var_export — 输出或返回一个变量的字符串表示

说明

var_export ( mixed $expression , bool $return = false ) : mixed

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

expression

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。

注释

Note:

当使用了return 参数时，本函数使用其内部输出缓冲，因此不能在 ob_start() 回调函数的内部使用。

更新日志

版本 说明
7.3.0 Now exports stdClass objects as an array cast to an object ((object) array( ... )), rather than using the nonexistent method stdClass::__setState(). The practical effect is that now stdClass is exportable, and the resulting code will even work on earlier versions of PHP.

范例

Example #1 var_export() 示例

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

以上例程会输出：

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

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

?>

以上例程会输出：

3.1

Example #2 输出类 stdClass (自 PHP 7.3.0 起)

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

var_export($person);

以上例程会输出：

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

Example #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);
?>

以上例程会输出：

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

Example #4 使用 __set_state() (自 PHP 5.1.0 起)

<?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);
?>

以上例程会输出：

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

注释

Note:

类型为 resource 的变量无法通过此函数输出。

Note:

var_export() does not handle circular references as it would be close to impossible to generate parsable PHP code for that. If you want to do something with the full representation of an array or object, use serialize().

Warning

When var_export() exports objects, the leading backslash is not included in the class name of namespaced classes for maximum compatibility.

Note:

To be able to evaluate the PHP generated by var_export(), all processed objects must implement the magic __set_state method. The only exception is stdClass, which is exported using an array cast to an object.

参见

User Contributed Notes

steven at nevvix dot com 13-Sep-2019 03:52
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 `=> [`
beverasrilakshmi at gmail dot com 01-May-2019 08:24
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);

?>
steven at nevvix dot com 18-Jun-2018 06:24
/**
 * 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;
}
Mark P 29-Jan-2016 09:09
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".
cpmcgrat()uci ! edu 27-Jul-2015 10:45
When trying to use __set_state() to rebuild a huge, tricky class use the following:

class Foo
{
    public $a;
    public $b;
    public $c;
    public $d;
    public $e;
    public $f;
    public $g;
    public $h;
    public $i;

    public function __set_state($array)
    {
        $obj = new ArrayConfig;
        foreach($array as $k => $v) {
            eval('$obj->'.$k.' = '.$v.';');
        }
        return $obj;
    }
}

This will return a reconstructed version of the class without having to manually type each individual object in the class manually (as shown in the __set_state() example)
dan at coders dot co dot nz 10-Jan-2014 02:11
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.
wyattstorch42 at outlook dot com 22-Dec-2013 10:11
If you call var_export() on an instance of stdClass, it attempts to export it using ::__set_state(), which, for some reason, is not implemented in stdClass.

However, casting an associative array to an object usually produces the same effect (at least, it does in my case). So I wrote an improved_var_export() function to convert instances of stdClass to (object) array () calls. If you choose to export objects of any other class, I'd advise you to implement ::__set_state().

<?php
/**
 * An implementation of var_export() that is compatible with instances
 * of stdClass.
 * @param mixed $variable The variable you want to export
 * @param bool $return If used and set to true, improved_var_export()
 *     will return the variable representation instead of outputting it.
 * @return mixed|null Returns the variable representation when the
 *     return parameter is used and evaluates to TRUE. Otherwise, this
 *     function will return NULL.
 */
function improved_var_export ($variable, $return = false) {
    if ($variable instanceof stdClass) {
        $result = '(object) '.improved_var_export(get_object_vars($variable), true);
    } else if (is_array($variable)) {
        $array = array ();
        foreach ($variable as $key => $value) {
            $array[] = var_export($key, true).' => '.improved_var_export($value, true);
        }
        $result = 'array ('.implode(', ', $array).')';
    } else {
        $result = var_export($variable, true);
    }

    if (!$return) {
        print $result;
        return null;
    } else {
        return $result;
    }
}

// Example usage:
$obj = new stdClass;
$obj->test = 'abc';
$obj->other = 6.2;
$obj->arr = array (1, 2, 3);

improved_var_export((object) array (
    'prop1' => true,
    'prop2' => $obj,
    'assocArray' => array (
        'apple' => 'good',
        'orange' => 'great'
    )
));

/* Output:
(object) array ('prop1' => true, 'prop2' => (object) array ('test' => 'abc', 'other' => 6.2, 'arr' => array (0 => 1, 1 => 2, 2 => 3)), 'assocArray' => array ('apple' => 'good', 'orange' => 'great'))
*/
?>

Note: This function spits out a single line of code, which is useful to save in a cache file to include/eval. It isn't formatted for readability. If you want to print a readable version for debugging purposes, then I would suggest print_r() or var_dump().
chudinov at yahoo dot com 29-Nov-2013 09:55
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)
 ?>
NitPicker 10-Jul-2013 04:33
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.
sergei dot solomonov at gmail dot com 04-Oct-2012 04:00
<?php
$closure = function(){};

var_export($closure);

// output: Closure::__set_state(array())
?>
kexianbin at diyism dot com 16-Sep-2012 02:33
to use my_var_export(), it is as beautiful as var_export() and as could deal with recursive reference as print_r():

<?php
function my_var_export($var, $is_str=false)
         {$rtn=preg_replace(array('/Array\s+\(/', '/\[(\d+)\] => (.*)\n/', '/\[([^\d].*)\] => (.*)\n/'), array('array (', '\1 => \'\2\''."\n", '\'\1\' => \'\2\''."\n"), substr(print_r($var, true), 0, -1));
          $rtn=strtr($rtn, array("=> 'array ('"=>'=> array ('));
          $rtn=strtr($rtn, array(")\n\n"=>")\n"));
          $rtn=strtr($rtn, array("'\n"=>"',\n", ")\n"=>"),\n"));
          $rtn=preg_replace(array('/\n +/e'), array('strtr(\'\0\', array(\'    \'=>\'  \'))'), $rtn);
          $rtn=strtr($rtn, array(" Object',"=>" Object'<-"));
          if ($is_str)
             {return $rtn;
             }
          else
              {echo $rtn;
              }
         }

?>
jodybrabec at gmail dot com 28-Mar-2012 05:52
WORKAROUND for error "Nesting level too deep - recursive dependency":
ob_start();
var_dump($GLOBALS);
$dataDump = ob_get_clean();
echo $dataDump;
Anonymous 11-Nov-2011 09:13
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>";
}
?>
laszlo dot heredy at gmail dot com 06-Oct-2010 01:57
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());
?>
4n4jmza02 at sneakemail dot com 17-Jun-2010 04:50
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.
john dot risken at gmail dot com 16-Jan-2010 03:53
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>";
}
?>
rarioj at gmail dot com 28-Oct-2009 10:43
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)

?>
ravenswd at gmail dot com 07-Jul-2009 10:32
(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.
ravenswd at gmail dot com 03-Jul-2009 05:21
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['firstelement'] = 'something'
... (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 . ' = ' . $varval . "<br>\n";
  else:
    foreach ($varval as $key => $val):
      recursive_print ($varname . "['" . $key . "']", $val);
    endforeach;
  endif;
}
?>
cmusicfan (at) gmail (daught) com 11-Jun-2009 09:19
Caution! var_export will add a backslash to single quotes (').

You may want to use stripslashes() to remove the mysteriously added backslashes.
stangelanda at arrowquick dot com 29-Jun-2007 04:20
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.
Glen 23-May-2007 05:47
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.
Zorro 04-Sep-2005 11:24
This function can't export EVERYTHING. Moreover, you can have an error on an simple recursive array:

$test = array();
$test["oops"] = & $test;

echo var_export($test);

=>

Fatal error:  Nesting level too deep - recursive dependency? in ??.php on line 59
linus at flowingcreativity dot net 04-Jul-2005 09:50
<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);
    }
}

?>
paul at worldwithoutwalls dot co dot uk 24-Nov-2004 11:22
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
?>
php_manual_note at bigredspark dot com 16-Oct-2003 12:43
[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...