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php bool false 跟数值 0

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Jun 13, 2016 pm 01:03 PM

echofalsephptestvar

php bool false 和数值 0

转：http://home.phpchina.com/space.php?uid=108724&do=blog&id=54899

PHP 是类型宽松的语言，这意味着会将布尔值 false 和整型值 0 视为相同（甚至 c 也把 0 和 false 视为等价）。可以使用一下脚本来确定 0 与布尔值?false 的等价性：

?$test_var = 0;
?if($test_var == false){
??echo "yes";
?}else{
??echo "no";
?}
?>?

输出：yes

_________________________________________________________________________________

?$test_var = 0;
?if($test_var !== false){
??echo "yes";
?}else{
??echo "no";
?}
?>

输出：yes

_________________________________________________________________

问题来了，布尔值 false 和整型值 0 明显是不同的。

PHP 有一个 gettype() 函数，得到变量的类型。可以使用 === 运算符（看好了，有三个等号）。和 == 运算符的区别在于该运算符同时比较数据的值和类型。

当终止条件中涉及不同的变量类型时，通过使用?===和?!==运算符进行强类型检查是很重要的。

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