var_export()

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

输出或返回一个变量的字符串表示

描述

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

您可以通过将函数的第二个参数设置为TRUE，从而返回变量的表示。

比较var_export()和var_dump().

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. 

/**
 * var_export() with square brackets and indented 4 spaces.
 */

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

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.

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. 

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

[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

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...

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

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: 

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.

(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:

will return:
$bigarray = array(
... (500 lines skipped) ...
     'mod' => 'charlie',
Whereas the routine below can be called with:

and it will return:
$bigarray = array()
... (500 lines skipped) ...
$bigarray['foo']['bar']['0']['somethingelse']['mod'] = 'charlie'
Here's the function:

will return:
$bigarray = array(
... (500 lines skipped) ...
     'mod' => 'charlie',
Whereas the routine below can be called with:

and it will return:
$bigarray['firstelement'] = 'something'
... (500 lines skipped) ...
$bigarray['foo']['bar']['0']['somethingelse']['mod'] = 'charlie'
Here's the function:

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