Question

哪个是正确的语法不等于operator

这 - ＆gt; ！=

if($ses_startdate != $startdate) {
                echo "I am true";
            }

或者这个 - ＆gt; ！==

if($ses_startdate !== $startdate) {
                echo "I am true";
            }

我一直在使用！= =之前它没有任何问题，但不是它创造了一些条件的问题，当我把它改为！=它工作正常..为什么会这样？

Answer 1

!==比!=更严格，!==也检查数据类型。例子：

$a = 1;
$b = '1';
$c = 1;
$d = TRUE;
// These are true:
$a == $c;
$a == $b;
$a === $c
$a == $d;
// but these are FALSE:
$a === $b;
$a === $d;

Answer 2

$a = '';
$b = false;

if($a != $b)
    //it is not executed since $a and $b are the same (empty) but have different types.

if($a !== $b)
    //it is executed, because $a is a string and $b is boolean, even though both of them represent the same value (empty).

所以，第三个=告诉php检查类型。

Answer 3

$ses_startdate != $startdate

在进行任何分析你的代码的比较时，习惯做相当于

的事情

var_dump ( $ses_startdate );

var_dump ( $startdate );

在该条件之前，将值转储到页面上或将其放入error_logs中，这样您就可以看到PHP正在评估变量的类型和值。

这是比较运算符的正确语法

3 个答案: