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HomeBackend DevelopmentPHP Tutorialphp中的global及GLOBALS的一些有关问题

php中的global及GLOBALS的一些问题

首先看一个简单例子

$a = 'scnjl';function test() {	global $a;	unset($a);}test();var_dump($a);function test1() {	unset($GLOBALS['a']);}test1();var_dump($a);

?这里输出的结果是:

string(5) "scnjl" NULL

可以看到其实global在函数中使用的时候,并没有直接用到变量$a,而是复制了一个指向$a的值的变量,所以当unset以后,全局变量$a并没有被unset,而$GLOBALS['a']直接代表了全局变量$a。

这是global 和 GLOBALS的区别吧。

?

今天在弄一个东西的时候发现全局变量在class中调用没有值,找了很久原因,原来是因为那个类里面的include的一个文件里面的值也不是全局变量,因为那个文件是被另一个函数所include,这样子造成类文件里面的include文件的变量也是局部变量。

例子:

test008.php

include 'test009.php';Class A {	var $name;	function __construct() {	}	function A() {		$this->__construct();	}	function test() {		var_dump($GLOBALS['var']);	}	function test1() {		$this->test();	}}$a = new A();

?test009.php

$var = 'scnjl';

?test010.php

class xx {	function __construct() {	}		function test() {		include 'test008.php';		$a->test1();	}}$xx = new xx();$xx->test();

?这个只是做个简单列子,其实test009.php里面的值是可以直接放到test008.php中的。

这里输出一个null。

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