时间：2021-07-01 10:21:17 帮助过：8人阅读
JS 里比较运算符比赋值运算符优先级高。于是 foo = 1 < 2 结果 foo = false；
PHP 里反过来，赋值运算符比比较运算符优先级高。于是 foo = 1 < 2 结果 foo = 1, 表达式为 false。为达到与上面同样的结果，需加上小括号
foo = (1 < 2)
附：PHP与JavaScript完整的运算符优先级
JS
The following table is ordered from highest (19) to lowest (0) precedence.
| Precedence | Operator type | Associativity | Individual operators |
|---|---|---|---|
| 19 | Grouping | n/a | ( … ) |
| 18 | Member Access | left-to-right | … . … |
| Computed Member Access | left-to-right | … [ … ] | |
| new (with argument list) | n/a | new … ( … ) | |
| 17 | Function Call | left-to-right | … ( … ) |
| new (without argument list) | right-to-left | new … | |
| 16 | Postfix Increment | n/a | … ++ |
| Postfix Decrement | n/a | … -- | |
| 15 | Logical NOT | right-to-left | ! … |
| Bitwise NOT | right-to-left | ~ … | |
| Unary Plus | right-to-left | + … | |
| Unary Negation | right-to-left | - … | |
| Prefix Increment | right-to-left | ++ … | |
| Prefix Decrement | right-to-left | -- … | |
| typeof | right-to-left | typeof … | |
| void | right-to-left | void … | |
| delete | right-to-left | delete … | |
| 14 | Exponentiation | right-to-left | … ** … |
| Multiplication | left-to-right | … * … | |
| Division | left-to-right | … / … | |
| Remainder | left-to-right | … % … | |
| 13 | Addition | left-to-right | … + … |
| Subtraction | left-to-right | … - … | |
| 12 | Bitwise Left Shift | left-to-right | … << … |
| Bitwise Right Shift | left-to-right | … >> … | |
| Bitwise Unsigned Right Shift | left-to-right | … >>> … | |
| 11 | Less Than | left-to-right | … < … |
| Less Than Or Equal | left-to-right | … <= … | |
| Greater Than | left-to-right | … > … | |
| Greater Than Or Equal | left-to-right | … >= … | |
| in | left-to-right | … in … | |
| instanceof | left-to-right | … instanceof … | |
| 10 | Equality | left-to-right | … == … |
| Inequality | left-to-right | … != … | |
| Strict Equality | left-to-right | … === … | |
| Strict Inequality | left-to-right | … !== … | |
| 9 | Bitwise AND | left-to-right | … & … |
| 8 | Bitwise XOR | left-to-right | … ^ … |
| 7 | Bitwise OR | left-to-right | … | … |
| 6 | Logical AND | left-to-right | … && … |
| 5 | Logical OR | left-to-right | … || … |
| 4 | Conditional | right-to-left | … ? … : … |
| 3 | Assignment | right-to-left | … = … |
… += … | |||
… -= … | |||
… **= … | |||
… *= … | |||
… /= … | |||
… %= … | |||
… <<= … | |||
… >>= … | |||
… >>>= … | |||
… &= … | |||
… ^= … | |||
… |= … | |||
| 2 | yield | right-to-left | yield … |
| 1 | Spread | n/a | ... … |
| 0 |
PHP
| Associativity | Operators | Additional Information |
|---|---|---|
| non-associative | clone new | clone and new |
| left | [ | array() |
| right | ** | arithmetic |
| right | ++ -- ~ (int) (float) (string) (array) (object) (bool) @ | types and increment/decrement |
| non-associative | instanceof | types |
| right | ! | logical |
| left | * / % | arithmetic |
| left | + - . | arithmetic and string |
| left | << >> | bitwise |
| non-associative | < <= > >= | comparison |
| non-associative | == != === !== <> <=> | comparison |
| left | & | bitwise and references |
| left | ^ | bitwise |
| left | | | bitwise |
| left | && | logical |
| left | || | logical |
| right | ?? | comparison |
| left | ? : | ternary |
| right | = += -= *= **= /= .= %= &= |= ^= <<= >>= => | assignment |
| left | and | logical |
| left | xor | logical |
| left | or | logical |
以上就介绍了PHP 与 JavaScript 的运算符优先级差异，包括了方面的内容，希望对PHP教程有兴趣的朋友有所帮助。