Variable handling Functions
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.
var_export
(PHP 4 >= 4.2.0, PHP 5)
var_export — Outputs or returns a parsable string representation of a variable
Description
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.
Parameters
- 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.
Note: This function uses internal output buffering with this parameter so it can not be used inside an ob_start() callback function.
Return Values
Returns the variable representation when the return parameter is used and evaluates to TRUE. Otherwise, this function will return NULL.
ChangeLog
| Version | Description |
|---|---|
| 5.1.0 | Possibility to export classes and arrays containing classes using the __set_state magic method. |
Examples
Example #1 var_export() Examples
<?php
$a = array (1, 2, array ("a", "b", "c"));
var_export($a);
?>
The above example will output:
array ( 0 => 1, 1 => 2, 2 => array ( 0 => 'a', 1 => 'b', 2 => 'c', ), )
<?php
$b = 3.1;
$v = var_export($b, true);
echo $v;
?>
The above example will output:
3.1
Example #2 Exporting classes since PHP 5.1.0
<?php
class A { public $var; }
$a = new A;
$a->var = 5;
var_export($a);
?>
The above example will output:
A::__set_state(array( 'var' => 5, ))
Example #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($a, true) . ';'); // $b = A::__set_state(array(
// 'var1' => 5,
// 'var2' => 'foo',
// ));
var_dump($b);
?>
The above example will output:
object(A)#2 (2) { ["var1"]=> int(5) ["var2"]=> string(3) "foo" }
Notes
Note: Variables of type resource couldn't be exported by this function.
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().
add a note
User Contributed Notesvar_export
stangelanda at arrowquick dot com
30-Jun-2007 01:20
30-Jun-2007 01:20
Glen
24-May-2007 02:47
24-May-2007 02:47
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-Mar-2007 02:44
21-Mar-2007 02:44
To import exported variable you can use this code:
<?
$str=file_get_contents('exported_var.str');
$var=eval('return '.$str.';')
// Now $val contains imported variable
?>
dosperios at dot gmail dot nospam do com
10-Oct-2006 08:19
10-Oct-2006 08:19
Here is a nifty function to export an object with var_export without the keys, which can be useful if you want to export an array but don't want the keys (for example if you want to be able to easily add something in the middle of the array by hand).
<?
function var_export_nokeys ($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-Aug-2006 12:48
30-Aug-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
05-Sep-2005 08:24
05-Sep-2005 08:24
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 06:50
04-Jul-2005 06:50
<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, $return);
}
}
?>
roman at DIESPAM dot feather dot org dot ru
18-Mar-2005 10:46
18-Mar-2005 10:46
Function that exports variables without adding any junk to the resulting string:
<?php
function encode($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-Nov-2004 08:22
24-Nov-2004 08:22
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-Jun-2004 06:53
11-Jun-2004 06:53
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-Oct-2003 09:43
16-Oct-2003 09:43
[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...