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这个比较运算符的正确语法是什么

php

1

Ibrahim Azhar Armar · 技术社区 · 15 年前

is not equal to运算符的正确语法是什么

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

或者这个->!==

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

我一直在用!==以前,它工作没有任何问题,但不是它创造了一些条件的问题,当我把它改为!=工作正常。。为什么?

3 回复 | 直到 15 年前

1

7

Lekensteyn 15 年前

!== != , !== 还要检查数据类型。示例:

$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;

2

1

Hugo Mota 15 年前

$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 =

3

1

Cups 15 年前

$ses_startdate != $startdate

当你做任何代码分叉的比较时,要习惯于做

var_dump ( $ses_startdate );

var_dump ( $startdate );