Analysis of the difference between var_export and var_dump in php_PHP tutorial

a var_dump
(PHP 3 >= 3.0.5, PHP 4, PHP 5)
var_dump -- Print 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.

Copy code 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 format is as follows:

Copy code The code 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)

two var_export
(PHP 4 >= 4.2.0, PHP 5)
var_export -- Export or return a string representation of a variable
Description
mixed var_export ( mixed expression [, bool return] )

This function returns structural information about the variables passed to the 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'))) This is no different from VAR_DUMP;

$ var =var_export(array('a','b',array('aa','bb','cc')),TRUE), after adding TRUE, it will not be printed out, but a variable will be given , so that it can be output directly;
echo $var; The output form at this time is similar to that printed by var_dump().
EG2

Copy code The code is as follows:

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

The output format is as follows:

Copy code The code is as follows:

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

The following are 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 Assign a variable directly 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,

Copy code The code is as follows:

error_log(var_export(yblog_mspconfiginit("ratings"),true)); always prints The return value of yblog_mspconfiginit("ratings") was NULL

, which led me to think that the connection to the DB could not be established, and I went down 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 , the code returned by var_export 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
Instance

Copy code The code is as follows:

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

Result:

Copy code The code is as follows:

resource(1) of type (yahoo_yblog)

NULL Another example:

Copy code The code is as follows:

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

Result:

Copy code The code is as follows:

resource(2) of type (stream)
NULL

http://www.bkjia.com/PHPjc/322468.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/322468.htmlTechArticlea var_dump (PHP 3 = 3.0.5, PHP 4, PHP 5) var_dump -- Print information about variables Description void var_dump ( mixed expression [, mixed expression [, ...]] ) This function displays information about a or...