What is the usage of global in php?

The usage of global in php is: 1. If you use global to declare, you can call variables outside the function; 2. Introduce the [$mk] variable outside the function, and global will be globalized here. The meaning of the variable.

The usage of global in php is:

To introduce a variable in java, it can be passed in the form of parameters , because Java uses object-oriented programming, but there are a lot of process-oriented things in PHP. For example, when an external variable is introduced into a function, under normal circumstances, this external variable is not passed in through parameters. , but introduced directly through global. But this global does not mean globalization. It is a test of the code.

$mk ="Test value"; 
 function initValue() 
 { 
 $va =$mk; 
 echo $va; 
 } 

The running result is:

- Undefined variable: mk

Because$mkis only defined in the method , so it is a different variable from$mkdefined before the method.$mkhas no value assigned, so an error is reported.

If it is declared with global, you can call variables outside the function.

$mk ="Test value"; 
 function initValue() 
 { 
 global $mk; 
 $va =$mk; 
 echo $va; 
 } 
 initValue(); 

The running result is: Test value. Here, global is used to introduce the$mkvariable outside the function.

In order to test global, here There is no meaning of globalizing variables, so I did another test.

$mk ="Test value"; 
 function initValue() 
 { 
 global $mk; 
 $va =$mk; 
 echo $va; 
 } 
 function initValue2() 
 { 
 $vc =$mk; 
 echo $vc; 
 } 
 initValue(); 
 initValue2(); 

The running results are: Test value and - Undefined variable: mk, which shows that even if global is used, it is only valid in a function, so the global here is just to introduce the upper variable

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