不等于 PHP 中的 != 和 !==
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Not equal to != and !== in PHP
提问by lawrence
I've always done this: if ($foo !== $bar)
我一直这样做： if ($foo !== $bar)
But I realized that if ($foo != $bar)is correct too.
但我意识到这if ($foo != $bar)也是正确的。
Double =still works and has always worked for me, but whenever I search PHP operators I find no information on double =, so I assume I've always have done this wrong, but it works anyway. Should I change all my !==to !=just for the sake of it?
Double=仍然有效并且一直对我有用，但是每当我搜索 PHP 运算符时，我都找不到有关 double 的信息=，所以我认为我一直都做错了，但无论如何它都有效。我应该改变我的所有!==来!=只是为了它的缘故？
回答by BoltClock
==and !=do not take into account the data type of the variables you compare. So these would all return true:
==并且!=不考虑您比较的变量的数据类型。所以这些都将返回 true：
'0' == 0
false == 0
NULL == false
===and !==dotake into account the data type. That means comparing a string to a boolean will neverbe true because they're of different types for example. These will all return false:
===并且!==也考虑到数据类型。这意味着将字符串与布尔值进行比较永远不会为真，因为例如它们的类型不同。这些都将返回 false：
'0' === 0
false === 0
NULL === false
You should compare data types for functions that return values that could possibly be of ambiguous truthy/falsy value. A well-known example is strpos():
您应该比较返回值可能是不明确的真/假值的函数的数据类型。一个众所周知的例子是strpos()：
// This returns 0 because F exists as the first character, but as my above example,
// 0 could mean false, so using == or != would return an incorrect result
var_dump(strpos('Foo', 'F') != false); // bool(false)
var_dump(strpos('Foo', 'F') !== false); // bool(true), it exists so false isn't returned
回答by Sandeep
!== should match the value and data type
!== 应该匹配值和数据类型
!= just match the value ignoring the data type
!= 只匹配忽略数据类型的值
$num = '1';
$num2 = 1;
$num == $num2; // returns true
$num === $num2; // returns false because $num is a string and $num2 is an integer
回答by Sandeep
$a !== $bTRUEif $ais not equal to $b, or they are not of the same type
$a !== $bTRUE如果$a不等于$b，或者它们的类型不同
Please Refer to http://php.net/manual/en/language.operators.comparison.php
请参阅 http://php.net/manual/en/language.operators.comparison.php
回答by Nick Craver
You can find the info here: http://www.php.net/manual/en/language.operators.comparison.php
你可以在这里找到信息：http: //www.php.net/manual/en/language.operators.comparison.php
It's scarce because it wasn't added until PHP4. What you have is fine though, if you know there may be a type difference then it's a much better comparison, since it's testing value andtype in the comparison, not just value.
它很少，因为它直到 PHP4 才被添加。不过，您所拥有的很好，如果您知道可能存在类型差异，那么这是一个更好的比较，因为它是在比较中测试值和类型，而不仅仅是值。
