PHP 與 JavaScript 的運算子優先順序差異

兩者優先順序大部分都一樣，比較（comparision）運算和賦值（assignment）運算有細微的差別。比較子有 >, <, >= 等等，賦值運算子有 =, +=, *= 等等。

JS 裡比較子比賦值運算子優先順序高。於是 foo = 1 < 2 結果 foo = false；

PHP 裡反過來，賦值運算子比比較子優先順序高。於是 foo = 1 < 2 結果 foo = 1, 運算式為 false。為達到與上面同樣的結果，需加上小括弧

foo = (1 < 2)

附：PHP與JavaScript完整的運算子優先順序

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

Operator Precedence

Associativity	Operators	Additional Information
non-associative	clone new	clone andnew
left	[	array()
right	**	arithmetic
right	++ -- ~ (int) (float) (string) (array) (object) (bool) @	types andincrement/decrement
non-associative	instanceof	types
right	!	logical
left	* / %	arithmetic
left	+ - .	arithmetic andstring
left	<< >>	bitwise
non-associative	< <= > >=	comparison
non-associative	== != === !== <> <=>	comparison
left	&	bitwise andreferences
left	^	bitwise
left	|	bitwise
left	&&	logical
left	||	logical
right	??	comparison
left	? :	ternary
right	= += -= *= **= /= .= %= &= |= ^= <<= >>= =>	assignment
left	and	logical
left	xor	logical
left	or	logical

以上就介紹了PHP 與 JavaScript 的運算子優先順序差異，包括了方面的內容，希望對PHP教程有興趣的朋友有所協助。

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