A pitfall of the logical operators and/or and |/& in PHP

I thought that and in PHP is the same, but it is written for readability and beauty. In fact, I am wrong. There is a deep hole in it! Run the following code: $ bAtrue; $ bBfalse; $ b1 $ bAand $ bB; $ b2 $ bA $ bB; var_dump ($ b1); $ b1truevar_dump ($ b2 ); $ b2false $ bAfalse; $ bB

I thought that and in PHP is the same, but it is written for readability and beauty. In fact, I am wrong. There is a deep hole in it! Run the following code: $ bA = true; $ bB = false; $ b1 = $ bA and $ bB; $ b2 = $ bA $ bB; var_dump ($ b1 ); // $ b1 = truevar_dump ($ b2); // $ b2 = false $ bA = false; $ bB =

I thought thatandAnd&&It is the same, but it is written for readability and beauty. In fact, I am wrong. There is a deep hole in it!

See the following code:

$bA = true;$bB = false;$b1 = $bA and $bB;$b2 = $bA && $bB;var_dump($b1); // $b1 = truevar_dump($b2); // $b2 = false$bA = false;$bB = true;$b3 = $bA or $bB;$b4 = $bA || $bB;var_dump($b3); // $b3 = falsevar_dump($b4); // $b4 = true

Strange,and/&&Andor/||The results are different. Where is the problem?

Let's look at another piece of code!

$bA = true;$bB = false;var_dump($bA and $bB); // falsevar_dump($bA && $bB); // false$bA = false;$bB = true;var_dump($bA or $bB); // truevar_dump($bA || $bB); // true

Even more strange, how is this right? So the problem may occur=Some google and documentation finally found the answer!

Operator priority

Operator priority

Through this table, we can seeand/&&Andor/||The priority of these operators is different.andAndorThe priority is lower=So the above Code is easy to understand, that is, assigning values first and then making anotherandOrorThe result of this operation is not stored, so the final result is incredible.

The following table lists the operators in order of precedence, with the highest-precedence ones at the top. Operators on the same line have equal precedence, in which case associativity decides grouping.

The following table lists the operation priorities. The higher the priority, the same row has the same priority.

Associativity	Operator	Additional information
Unassociated	Clone new	Clone and new
Left	[	Array
Left	**	Arithmetic
Right	++ -~ (Int) (float) (string) (array) (object) (bool )@	Type and auto-increment/auto-Increment
Unassociated	Instanceof	Type
Right	!	Logical operation
Left	*/%	Arithmetic
Left	+ -.	Arithmetic and string
Left	<>	Bitwise operation
Unassociated	<=> =	Comparison
Unassociated	=! ===! ==<>	Comparison
Left	&	Bitwise operation and reference
Left	^	Bitwise operation
Left	| Bitwise operation
Left	&&	Logical operation
Left	| Logical operation
Left	? :	Ternary Condition Selection
Right	= + =-= * =/=. = % = & =	==<<=>>=> | Assign a value
Left	And	Logical operation
Left	Xor	Logical operation
Left	Or	Logical operation
Left	,	Many Uses

Summary

Exercise cautionand,orAndxorLogical operators of, avoid and assign values and&&And||To avoid unnecessary logical errors.

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