Interpretation of Global keyword reference for PHP global variables

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Interpretation of Global keyword reference for PHP global variables_PHP tutorial

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Jul 13, 2016 pm 05:15 PM

global php one time introduce overall situation about Keywords variable Quote article of Simple Interpretation

This article will give you a brief introduction to the PHP global variable Global keyword reference. Although the comment is extremely short compared to the article, the principle is explained very clearly and is easy to understand, especially for It is worth summarizing for those who have some basic knowledge of language. Without further ado, let’s get down to the topic:

Quoting the explanation of $GLOBALS in the PHP manual:

Global variable: $GLOBALS
Note: $GLOBALS is available in PHP 3.0.0 and later.

An array consisting of all defined global variables. The variable name is the index into the array.

This is a "superglobal", or can be described as an automatic global variable.
In other words, $var1 and $GLOBALS['var1'] in the above code refer to the same variable, not 2 different variables!

Global variable example

The code is as follows

代码如下	复制代码
$pangbu = "pangbu"; function demo (){ global $pangbu; echo $pangbu; } demo(); ?>

Copy code

$pangbu = "pangbu";

function demo (){

global $pangbu;

echo $pangbu;

}

代码如下	复制代码
$url = "www.bKjia.c0m"; function get_url(){ echo "The blog is".$url; //这里获取不到$url,因为它只是一个未定义的局部变量 } get_url(); ?>

demo();
?>

代码如下	复制代码
$url = "www.bKjia.c0m"; function get_url(){ global $url; echo "The blog url is ".$url; } get_url(); ?>

Explanation

In fact, global $pangbu ; is the abbreviation of $pangbu = &$_GLOBAL['pangbu '],

代码如下	复制代码
$url = "www.bKjia.c0m"; function get_url(){ echo "The blog url is ".$GLOBALS['url']; } get_url(); ?>

It means that $pangbu is a reference of $_GLOBAL['pangbu ']. As for how to use the reference, $pangbu is used.

Some notes of my own I never figured out how to use global before. Although I knew how to use it, I was always confused. Now I finally figured it out. . In order to learn more about Global's applications, please see the following php case:

The code is as follows

Copy code

$url = "www.bKjia.c0m";<🎜> Function get_url(){<🎜> echo "The blog is".$url; //$url cannot be obtained here because it is just an undefined local variable<🎜> }<🎜> Get_url();<🎜> ?> The above example will report a notice error!

The code is as follows

Copy code

$url = "www.bKjia.c0m";<🎜> function get_url(){<🎜> global $url;<🎜> echo "The blog url is ".$url;<🎜> }<🎜> get_url();<🎜> ?> The above usage is correct. After declaring a global variable in a function, all reference variables of any variable will point to the global variable! It is also necessary to mention that the global array $GLOBALS[] can be rewritten using the above example as follows:

The code is as follows

Copy code

$url = "www.bKjia.c0m";<🎜> function get_url(){<🎜> echo "The blog url is ".$GLOBALS['url'];<🎜> }<🎜> get_url();<🎜> ?> Note that global declared variables cannot be copied, such as global $url = "www.hzhuti.com"; This is wrong

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