The use and difference between global static and $GLOBALS in php

The use and difference between global static and $GLOBALS in php_PHP tutorial

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Release： 2016-07-13 17:14:43

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This article summarizes and introduces the use and differences of global static and $GLOBALS in PHP. Friends who need to understand the differences between them can refer to it.

1.global works on the entire page.

Example 1

The code is as follows

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代码如下	复制代码
global $var1,$var2;

global $var1,$var2;

is a reference to an external variable with the same name, and the scope of the variable itself is still within the function body. Changing the values of these variables will naturally change the external variables with the same name. But once & is used, the variable will no longer be a reference with the same name.

代码如下	复制代码
$var1 = 1;$var2 = 2; function test(){ global $var1,$var2; // 作用范围在函数体内 $var1 = 3;} test(); echo $var1; ?>

The code is as follows

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$var1 = 1;$var2 = 2;

function test(){

global $var1,$var2;

// Scope is within the function body

$var1 = 3;}

代码如下	复制代码
$glpbal $a; $a=123; function f() { echo $a; //错误, }

test();

echo $var1;

代码如下	复制代码
function f() { global $a; $a=123; } f(); echo $a; //正确,可以使用

The result is 3.

Because it is a reference with the same name

The PHP Global variables defined inside the function body can be used outside the function body. The global variables defined outside the function body cannot be used inside the function body.

The code is as follows

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$glpbal $a; $a=123; function f() { echo $a; //Error, }

代码如下

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/*
*author:ajax123
*qq:283400245
*/
class person{
static$name="ajax123";//static声明静态属性
static$age=25;//static声明静态属性
static$address="北京";//static声明静态属性
function song(){
echo "My name is : ".self::$name."
";//类内部:通过通过self 类访问静态属性
echo "I am ".self::$age."
";//类内部:通过通过self 类访问静态属性
echo "I live in ".self::$address."
";//类内部:通过self 类访问静态属性
}
}
echoperson::$name."
";//类外部:通过类名person访问静态属性
echoperson::$age."
";//类外部:通过类名person访问静态属性
echoperson::$address."
";//类外部:通过类名person访问静态属性
?>

Look at the following example

The code is as follows	Copy code
function f() { global $a; $a=123; } f(); echo $a; //Correct, you can use

2.static only works within functions and classes. global and $GLOBALS are basically used the same, but are quite different in actual development. global generates an alias variable in the function that points to the external variable of the function, instead of the real external variable of the function. Once the address pointed to by the alias variable is changed, some unexpected situations will occur, Example 1.

The code is as follows

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";//Internal class: access static properties through the self class echo "I am ".self::$age."
";//Inside the class: access static properties through the self class echo "I live in ".self::$address."
";//Inside the class: access static properties through the self class } } echoperson::$name."
";//External class: access static properties through class name person echoperson::$age."
";//External class: access static properties through class name person echoperson::$address."
";//External class: access static properties through class name person ?>

$GLOBALS[] is indeed called an external variable, and it will always be consistent inside and outside the function

Example #1 $GLOBALS Example

echo '$foo in global scope: ' . $GLOBALS["foo"] . "n";

The code is as follows

代码如下

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function test() {
$foo = "local variable";

echo '$foo in global scope: ' . $GLOBALS["foo"] . "n";
echo '$foo in current scope: ' . $foo . "n";
}

$foo = "Example content";
test();
?>

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function test() {

$foo = "local variable";