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Funktionen zur Behandlung von Variablen

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var_export

(PHP 4 >= 4.2.0, PHP 5)

var_exportOutputs or returns a parsable string representation of a variable

Beschreibung

mixed var_export ( mixed $expression [, bool $return = false ] )

var_export() gets structured information about the given variable. It is similar to var_dump() with one exception: the returned representation is valid PHP code.

Parameter-Liste

expression

The variable you want to export.

return

If used and set to TRUE, var_export() will return the variable representation instead of outputing it.

Hinweis:

Diese Funktion benutzt intern Ausgabenpufferung mit diesem Parameter und kann daher nicht in einer ob_start()-Callbackfunktion eingesetzt werden.

Rückgabewerte

Returns the variable representation when the return parameter is used and evaluates to TRUE. Otherwise, this function will return NULL.

Changelog

Version Beschreibung
5.1.0 Possibility to export classes and arrays containing classes using the __set_state magic method.

Beispiele

Beispiel #1 var_export() Examples

<?php
$a 
= array (12, array ("a""b""c"));
var_export($a);
?>

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

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

$b 
3.1;
$v var_export($btrue);
echo 
$v;

?>

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

3.1

Beispiel #2 Exporting classes since PHP 5.1.0

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

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

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

Beispiel #3 Using __set_state (since PHP 5.1.0)

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

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

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

Anmerkungen

Hinweis:

Variables of type resource couldn't be exported by this function.

Hinweis:

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().

Siehe auch

  • print_r() - Gibt Variablen-Informationen in lesbarer Form aus
  • serialize() - Erzeugt eine speicherbare Repräsentation eines Wertes
  • var_dump() - Gibt alle Informationen zu einer Variablen aus


18 BenutzerBeiträge:
- Beiträge aktualisieren...
laszlo dot heredy at gmail dot com
6.10.2010 22:57
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
18.06.2010 1:50
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
17.01.2010 0:53
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
29.10.2009 7:43
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
7.07.2009 19:32
(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
3.07.2009 14:21
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
12.06.2009 6:19
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
30.06.2007 1:20
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
24.05.2007 2:47
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.
niq
21.03.2007 14:44
To import exported variable you can use this code:

<?
$str
=file_get_contents('exported_var.str');
$var=eval('return '.$str.';')
// Now $val contains imported variable
?>
dosperios at dot gmail dot nospam do com
10.10.2006 20:19
Here is a nifty function to export an object with var_export without the keys, which can be useful if you want to export an array but don't want the keys (for example if you want to be able to easily add something in the middle of the array by hand).

<?
function var_export_nokeys ($obj, $ret=false) {
   
$retval = preg_replace("/'?\w+'?\s+=>\s+/", '', var_export($obj, true));
    if (
$ret===true) {
        return
$retval;
    } else {
        print
$retval;
    }
}
?>

Works the same as var_export obviously. I found it useful, maybe someone else will too!
nobody at nowhere dot de
30.08.2006 12:48
Here is a bit code, what will read an saved object and turn it into an array.
Please note: It is very lousy style. Only an an idea.

$data = file_get_contents("test.txt");
$data = preg_replace('/class .*{/im', 'array (', $data);
$data = preg_replace('/\}/im', ')', $data);
$data = preg_replace('/var /im', '', $data);
$data = preg_replace('/;/im', ',', $data);
$data = preg_replace('/=/im', '=>', $data);
$data = preg_replace('/=>>/im', '=>', $data);
$data = preg_replace('/\$(.*?) /im', '"$1"', $data);
eval('$O = ' . $data . ';');
print_r($O);
Zorro
5.09.2005 8:24
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
4.07.2005 18:50
<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);
    }
}

?>
roman at DIESPAM dot feather dot org dot ru
18.03.2005 22:46
Function that exports variables without adding any junk to the resulting string:
<?php
function encode($var){
    if (
is_array($var)) {
       
$code = 'array(';
        foreach (
$var as $key => $value) {
           
$code .= "'$key'=>".encode($value).',';
        }
       
$code = chop($code, ','); //remove unnecessary coma
       
$code .= ')';
        return
$code;
    } else {
        if (
is_string($var)) {
            return
"'".$var."'";
        } elseif (
is_bool($code)) {
            return (
$code ? 'TRUE' : 'FALSE');
        } else {
            return
'NULL';
        }
    }
}

function
decode($string){
    return eval(
'return '.$string.';');
}
?>
The resulting string can sometimes be smaller, that output of serialize(). May be useful for storing things in the database.
paul at worldwithoutwalls dot co dot uk
24.11.2004 20:22
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
?>
aidan at php dot net
11.06.2004 6:53
This functionality is now implemented in the PEAR package PHP_Compat.

More information about using this function without upgrading your version of PHP can be found on the below link:

http://pear.php.net/package/PHP_Compat
php_manual_note at bigredspark dot com
16.10.2003 9:43
[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...



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