Detailed explanation of PHP operator priority order-PHP Tutorial-php.cn

Detailed explanation of PHP operator priority order

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Release： 2023-03-07 15:08:02

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When we talked about PHP logical operators earlier, we mentioned the priority of PHP operators. The so-called operator priority refers to which operator in the expression is calculated first and which one is calculated later. It seems that the result

of the expression 1 + 5 * 3 is 16 instead of 18 because the multiplication sign ("*") has a higher priority than the plus sign ("+"). If necessary, parentheses can be used to force a priority change. For example: (1 + 5) * 3 has the value 18.

The rules followed by PHP operators in operations are: operations with higher priority are executed first, and operations with lower priority are executed later. If they have the same priority, they are executed in order from left to right, for example , "-" is a left-joint, then 1 - 2 - 3 is equivalent to (1 -

2) - 3 and the result is -4. On the other hand, "=" is a right-joint, so $a = $b = $c is equivalent to $a = ($b = $c).

Detailed explanation of PHP operator priority order The operators in the brackets are executed first. The use of brackets, even if it is not necessary, clearly indicates the order of operations through the pairing of brackets, rather than relying on operator priority and associativity. To decide, it can improve the readability of the code.

The table lists operators from high to low precedence. Operators in the same line have the same precedence, and the direction in which they are combined determines the order of evaluation.

/ %-.Bitwise OperatorNoneComparison operators ;=>^|&&Logical operatorComparison operatorTernary operator += ‐ ## |= ‐ or Logical operatorsWith so many priority levels, it is unrealistic to remember them all clearly. Yes, it’s not necessary. If the expression you write is very complex and contains a lot of running symbols, don’t use parentheses. Think of it like this:

<?php
$a and (($b !=$c) or (5*(50-$d)));
?>

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Combining direction	Operator	Additional information
None	clone new	clone and new
left	[	array ()
Right	**	Arithmetic operator
Right	##++ -- ~ (int) ‐ #(string) (array) (object) ’ ’s ’ s ’ ‐ ‐ P P S P C P C P C C P S C P S C S P S C S P S P S P S P S P S P S P S P S P S P S P S P D S N M ／DecreasingNoneinstanceof	Type
right	!	Logical operator
left	*
Arithmetic operator	left+
Arithmetic operators and string operators	##left >>
		>=
	None== != ===	!==
Comparison operator	left&bit operation Symbols and references left
bit operators	left
bit operator	left
Logical operator	##left	\|\|
	left	??
	left	? :
	Right	=
-=	= *=	&=
^=	#Assignment operatorleftandLogical operatorleftxorlogical operatorleft

This will reduce the possibility of logic errors	Sometimes using parentheses can enhance the readability of the code. For example, the following: <?php $a = 3 * 3 % 5; // (3 * 3) % 5 = 4 //三元运行的结合 $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 ?> Copy after login

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