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PHP:empty,isset,is_null,array(零),array(),array(""),0,"0""""null"NULL的总结

WBOY
WBOYOriginal
2016-06-13 12:23:30805browse

PHP:empty,isset,is_null,array(0),array(),array(""),0,"0","","null",NULL的总结

通过下面这个程序来检测

$a=0;if(empty($a)){	echo "yes|";}else{	echo "no|";}if(isset($a)){	echo "yes|";}else{	echo "no|";}if(is_null($a)){	echo "yes|";}else{	echo "no|";}if($a){	echo "yes|";}else {	echo "no|";}

那么$a 分别取不同值的时候结果如下



总结:

empty的情况

1变量的值为空 $var = “”;

2变量的值为字符串0或者数字0  $var = 0 ; 或者$var =”0″

3变量的值为flase $var= flase;

4凡是为NULL的 都为空

5空数组  $arr =array();

6变量只定义不赋值$var;

isset的情况

查看一个变量是否已经被设置并且不为空(Determine if a variable is set and is not NULL)

is_null

判断null

判断是否为假

1变量的值为空 $var = “”;

2变量的值为字符串0或者数字0  $var = 0 ; 或者$var =”0″

3变量的值为flase $var= flase;

4凡是为NULL的 都为空

5空数组  $arr =array();

6变量只定义不赋值$var;

这些全假

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