Introduction to PHP Operator precedence

The operator precedence specifies how tightly the two expressions are bound. For example, the result of the expression 1 + 5 * 3 is that It is because multiplication sign ("*") has a higher priority than the plus sign ("+"). You can use parentheses to force a change of precedence if necessary. For example:(1 + 5) * 3 is the value of . If the operator has the same precedence, the left-to-right leftist order is used.

The following table lists the precedence of operators from high to low. Operators in the same row have the same precedence, at which point their binding direction determines the order of evaluation.

Operator Precedence

Combination Direction	operator	Additional Information
Non-binding	Clone new	Clone and new
Left	[	Array ()
Non-binding	++ --	Increment/decrement operator
Non-binding	~-(int) (float) (string) (array) (object) (BOOL) @	Type
Non-binding	instanceof	Type
Right combination	!	logical operators
Left	* / %	Arithmetic operators
Left	+ - .	Arithmetic operators and string operators
Left	<< >>	Bitwise operators
Non-binding	< <= > >= <>	Comparison operators
Non-binding	== != === !==	Comparison operators
Left	&	Bitwise operators and references
Left	^	Bitwise operators
Left	|	Bitwise operators
Left	&&	logical operators
Left	||	logical operators
Left	? :	Ternary operators
Right	= + = = *=/=. =%= &= |= ^= <<= >>=	Assignment operators
Left	and	logical operators
Left	Xor	logical operators
Left	Or	logical operators
Left	,	Used in many places

Leftist indicates that the expression is evaluated from left to right and vice versa.

Example #1 Combination Direction

<?php$a = 3 * 3 5; (3 * 3)% 5 = 4$a = true? 0:true? 1:2; (true? 0:true)? 1:2 = 2$a = 1; $b = 2; $a = $b + = 3; $a = ($b + = 3), $a = 5, $b = 5?> use parentheses to enhance the readability of your code.

Note:

Although = is lower than most other operators, PHP still allows an expression similar to the following:if (! $a = foo ()), in this case foo () The return value is assigned to the $a .

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Introduction to PHP Operator precedence