Analysis of the difference between var_export and var_dump in php

This article mainly shares with you the analysis of the difference between var_export and var_dump in php, hoping to help everyone.

var_dump (PHP 3 >= 3.0.5, PHP 4, PHP 5)

var_dump -- Print related information about variables
Description

void var_dump ( mixed expression [, mixed expression [, ...]] )

This function displays structural information about one or more expressions, including the type and value of the expression. Arrays will expand values ​​recursively, showing their structure through indentation.

The code is as follows:

$data = array ('name' => 'abc', 'job' => 'programmer','a'=>array('aa','cc','bb'));
$data = var_dump($data,TRUE); 
echo $data;

The output form is as follows:

array(3) { 
["name"]=> 
string(3) "abc" 
["job"]=> 
string(10) "programmer" 
["a"]=> 
array(3) { 
[0]=> 
string(2) "aa" 
[1]=> 
string(2) "cc" 
[2]=> 
string(2) "bb" 
} 
} 
bool(true)

二var_export

(PHP 4 >= 4.2.0, PHP 5) 
var_export -- 输出或返回一个变量的字符串表示 
描述 
mixed var_export ( mixed expression [, bool return] )

This function returns the information about the transfer Gives the structure information of the variables of this function. It is similar to var_dump(), except that the representation returned is legal PHP code.
You can return a representation of a variable by setting the second parameter of the function to TRUE.
EG:

var_export(array('a','b',array('aa','bb','cc'))) 这种与VAR_DUMP没什么区别; 
$var =var_export(array('a','b',array('aa','bb','cc')),TRUE)，加上TRUE后，不会再打印出来，而是给了一个变量，这样就可以直接输出;
echo $var;此时输出来的形式与var_dump()打印的相似。

EG2

$data = array ('name' => 'abc', 'job' => 
'programmer','a'=>array('aa','cc','bb'));
$data = var_export($data,TRUE); echo $data;

The output format is as follows:

array ( 
'name' => 'abc', 'job' =>
 'programmer', 'a' => array 
 ( 0 => 'aa', 1 => 'cc', 2 => 'bb', ),
  )

The following is supplementary information:

error_log(var_export(yblog_mspconfiginit("ratings"),true));

Cause of the problem

var_export must return legal PHP code. In other words, the code returned by var_export can be directly assigned to a variable as PHP code. And this variable will get the same type of value as var_export. However, when the variable type is resource, it cannot be copied simply. Therefore, when the variable of var_export is of resource type, var_export will return NULL.

Problem Discovery

When tracking yratings_get_targets,

error_log(var_export(yblog_mspconfiginit("ratings"),true));老是打印出yblog_mspconfiginit(“ratings”)的返回是NULL

led me to think that the connection to the DB could not be established, and I took the wrong path for a day.
Finally, I discovered that this is one of the differences between var_export and var_dump

This is:
Cause of the problem
var_export must return legal php code, that is, var_export returns The code can be directly used as PHP code to assign a variable. And this variable will get the same type of value as var_export
However, when the variable type is resource, it cannot be simply copied. Therefore, when the variable of var_export is of resource type, var_export will return NULL

Example

$res = yblog_mspconfiginit("ratings"); 
var_dump($res); 
var_export($res);

Result:

The code is as follows:

resource(1) of type (yahoo_yblog)

NULL Another example:

The code is as follows:

$res = fopen('status.html', 'r'); 
var_dump($res); 
var_export($res);

Result:

resource(2) of type (stream) 
NULL

Related recommendations:

php var_export function example explanation

##var_export function summary and comparison with var_dump

var_export and var_dump usage introduction_PHP tutorial

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