Analysis of the difference between global variables global and $GLOBALS[] in PHP

Analysis of the difference between global variables global and $GLOBALS[] in PHP_PHP Tutorial

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Release： 2016-07-21 15:17:11

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< ?php $var1 = 1; function test(){
unset($GLOBALS['var1']);
}

test(); echo $var1; ?> Because $var1 was deleted, nothing is printed.

Example 2:

Copy code

The code is as follows:

$var1 = 1;
function test(){
global $var1;
unset($var1);

} test(); echo $var1; ?>

Unexpectedly printed 1. It proves that only the alias reference is deleted, and its value has not been changed in any way. 


2. Explanation 

global $var is actually &$GLOBALS['var'], which is just an alias for calling external variables. 
$var1 and $GLOBALS['var1'] in the above code refer to the same variable, not two different variables. 
PHP’s global variables are a little different from C language. In C language, global variables automatically take effect in functions unless covered by local variables. This can cause problems, as someone might carelessly mutate a global variable. Global variables in PHP must be declared as global using global when used in functions. 
PHP’s Global variable is used to define global variables, but this global variable does not apply to the entire website, but to the current page, including all files in include or require. 

3. Conclusion

1.$GLOBALS['var'] is the external global variable itself
2.global $var is the reference or pointer of the same name of the external $var .

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1. Comparative Example 1: Copy the code as follows: ?php $var1 = 1; function test(){ unset($GLOBALS['var1']); } test(); echo $var1; ? Because $var1 was deleted, something...

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