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var_export

(PHP 4 >= 4.2.0, PHP 5)

var_exportImprime o devuelve una representación string de una variable analizable

Descripción

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

var_export() obtiene información estructurada sobre la variable dada. Es similar a la función var_dump() con una excepción: la representación devuelta es código PHP válido.

Parámetros

expression

La variable que desea exportar.

return

Si es usada y se define como TRUE, var_export() devolverá la representación de la variable en lugar de imprimirla.

Valores devueltos

Devuelve la representación de la variable cuando el parámetro return es utilizado y evaluado como TRUE. En caso contrario, esta función devolverá NULL.

Notas

Nota:

Cuando el parámetro return se usa, esta función utiliza el almacenamiento en búfer de salida interno, por lo que no puede usarse dentro de una función de llamada de retorno ob_start().

Historial de cambios

Versión Descripción
5.1.0 Posibilidad de exportar las clases y los arrays que contienen las clases utilizando el método mágico __set_state.

Ejemplos

Ejemplo #1 Ejemplos de var_export()

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

El resultado del ejemplo sería:

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

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

?>

El resultado del ejemplo sería:

3.1

Ejemplo #2 Exportación de clases a partir de PHP 5.1.0

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

El resultado del ejemplo sería:

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

Ejemplo #3 Uso de __set_state (a partir de PHP 5.1.0)

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

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

El resultado del ejemplo sería:

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

Notas

Nota:

Las variables de tipo resource no pueden ser exportadas por esta función.

Nota:

var_export() no maneja referencias circulares ya que sería prácticamente imposible generar código PHP interpretable en tal caso. Si desea trabajar con la representación completa de una matriz u objeto, use serialize().

Advertencia

Cuando var_export() exporta objectos, la barra diagonal no se incluye en el nombre de clases que pertencen a un namespace para mantener compatibilidad.

Ver también

  • print_r() - Imprime información legible para humanos sobre una variable
  • serialize() - Genera una representación apta para el almacenamiento de un valor
  • var_dump() - Muestra información sobre una variable

add a note add a note

User Contributed Notes 22 notes

up
7
Anonymous
2 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>";
}
?>
up
6
linus at flowingcreativity dot net
9 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);
    }
}

?>
up
4
Glen
7 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.
up
3
laszlo dot heredy at gmail dot com
3 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());
?>
up
2
rarioj at gmail dot com
4 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)

?>
up
2
ravenswd at gmail dot com
5 years ago
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;
}
?>
up
3
php_manual_note at bigredspark dot com
10 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...
up
1
wyattstorch42 at outlook dot com
8 months ago
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().
up
1
john dot risken at gmail dot com
4 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>";
}
?>
up
2
chudinov at yahoo dot com
9 months 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)
?>
up
1
stangelanda at arrowquick dot com
7 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.
up
1
dan at coders dot co dot nz
8 months 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.
up
0
NitPicker
1 year 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.
up
0
sergei dot solomonov at gmail dot com
1 year ago
<?php
$closure
= function(){};

var_export($closure);

// output: Closure::__set_state(array())
?>
up
0
jodybrabec at gmail dot com
2 years ago
WORKAROUND for error "Nesting level too deep - recursive dependency":
ob_start();
var_dump($GLOBALS);
$dataDump = ob_get_clean();
echo $dataDump;
up
0
4n4jmza02 at sneakemail dot com
4 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.
up
0
ravenswd at gmail dot com
5 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.
up
-1
Zorro
9 years ago
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
up
-1
paul at worldwithoutwalls dot co dot uk
9 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
?>
up
-2
cmusicfan (at) gmail (daught) com
5 years ago
Caution! var_export will add a backslash to single quotes (').

You may want to use stripslashes() to remove the mysteriously added backslashes.
up
-3
kexianbin at diyism dot com
1 year ago
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;
              }
         }

?>
up
-5
nobody at nowhere dot de
8 years ago
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);
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