AND [和] && 之间的区别

发布于 2024-11-30 14:23:50 字数 274 浏览 1 评论 0原文

鉴于以下陈述：

if($value && array_key_exists($value, $array)) {

         $hello['world'] = $value;

        }

最好使用逻辑运算符 AND 与 && 相对？

原文

Given the statement:

if($value && array_key_exists($value, $array)) {

         $hello['world'] = $value;

        }

Would it be best to use the logical operator AND as opposed to &&?

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葬シ愛 2024-12-07 14:23:50

他们自己也做同样的事情。所以 a && b 的含义与 a 和 b 相同。但是，它们并不相同，因为 && 的优先级高于 and。有关更多信息，请参阅文档。

此示例显示了差异：

// The result of the expression (false && true) is assigned to $e
// Acts like: ($e = (false && true))
$e = false && true;

// The constant false is assigned to $f and then true is ignored
// Acts like: (($f = false) and true)
$f = false and true;

On their own, they do exactly the same. So a && b means the same than a and b. But, they are not the same, as && has a higher precedence than and. See the docs for further information.

This example here shows the difference:

// The result of the expression (false && true) is assigned to $e
// Acts like: ($e = (false && true))
$e = false && true;

// The constant false is assigned to $f and then true is ignored
// Acts like: (($f = false) and true)
$f = false and true;

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水波映月 2024-12-07 14:23:50

您提供的链接有一个注释：

“and”和“or”运算符有两种不同变体的原因是它们的操作优先级不同。（请参阅运算符优先级。）

在您的情况下，由于它是唯一的运算符，因此取决于您，但它们并不完全相同。

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最舍不得你 2024-12-07 14:23:50

它们在条件语句中是相同的，但在条件赋值时要小心：

// The result of the expression (true && false) is assigned to $g
// Acts like: ($g = (true && false))
$g = true && false;

// The constant true is assigned to $h and then false is ignored
// Acts like: (($h = true) and false)
$h = true and false;

并且

// The result of the expression (false || true) is assigned to $e
// Acts like: ($e = (false || true))
$e = false || true;

// The constant false is assigned to $f and then true is ignored
// Acts like: (($f = false) or true)
$f = false or true;

来自逻辑运算符 您链接到的手册。

They are the same in conditional statements, but be careful on conditional assignments:

// The result of the expression (true && false) is assigned to $g
// Acts like: ($g = (true && false))
$g = true && false;

// The constant true is assigned to $h and then false is ignored
// Acts like: (($h = true) and false)
$h = true and false;

and

// The result of the expression (false || true) is assigned to $e
// Acts like: ($e = (false || true))
$e = false || true;

// The constant false is assigned to $f and then true is ignored
// Acts like: (($f = false) or true)
$f = false or true;

From the Logical Operators manual you linked to.

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