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PHP - Operators Precedence



PHP Operators Precedence

Operator precedence (order of operations) is a collection of rules that reflect conventions about which procedures to perform first in order to evaluate a given expression.

For example, multiplication has higher precedence than addition. Thus, the expression 1 + 2 × 3 is interpreted to have the value 1 + (2 × 3) = 7, and not (1 + 2) × 3 = 9. When exponent is used in the expression, it has precedence over both addition and multiplication. Thus 3 + 52 = 28 and 3 × 52 = 75.

Operator Associativity

Operator associativity is the direction in which an expression is evaluated. For example:

$x = 10;
$y = 20;

//associativity of = operator is
//Left to Right, hence x will become 20
$x = $y;

As the associativity of = is left to right. Hence x is assigned the value of y.

Example:

The example below illustrates the operator precedence in PHP.

<?php
//evaluates 5 * 2 first
$retval1 = 15 - 5 * 2;

//above expression is equivalent to
$retval2 = 15 - (5 * 2);

//forcing compiler to evaluate 15 - 5 first
$retval3 = (15 - 5) * 2;

echo "15 - 5 * 2 = $retval1 \n";
echo "15 - (5 * 2) = $retval2 \n";
echo "(15 - 5) * 2 = $retval3 \n";
?>

The output of the above code will be:

15 - 5 * 2 = 5
15 - (5 * 2) = 5
(15 - 5) * 2 = 20

PHP Operators Precedence Table

The following table lists the precedence and associativity of PHP operators. Operators are listed top to bottom, in descending precedence. Operators with higher precedence are evaluated before operators with relatively lower precedence. When operators have the same precedence, associativity of the operators determines the order in which the operations are performed.

PrecedenceOperatorDescriptionAssociativity
25cloneclone operatorNA
newnew operator
24**ExponentiationRight to Left
23++a  --aPrefix increment, Prefix decrementNA
a++  a--Postfix increment, Postfix decrement
+a  -aUnary plus, Unary minus
~Bitwise NOT
(int)  (float)  (string)  (array)  (object)  (bool)Type casting
@Error control operator
22instanceofType operatorLeft to Right
21!Logical NOTNA
20*  /  %Multiplication, Division, RemainderLeft to Right
19+  -  .Addition, Subtraction, Concatenating operator (. prior to PHP 8.0.0)
18<<  >>Bitwise left shift and right shift
17.Concatenating operator (as of PHP 8.0.0)
16<  <=  >  >=Less than, Less than or equal, Greater than, and Greater than or equalnon-associative
15==  !=Equality, Inequality
===  !==Strict Equality, Strict Inequality
<>  <=>Inequality, Spaceship operator
14&Bitwise AND and reference operatorLeft to Right
13^Bitwise XOR
12|Bitwise OR
11&&Logical AND
10||Logical OR
9??Null coalescing operatorRight to Left
8a?b:cConditional (ternary) operatorNon-associative (Left to Right associative prior to PHP 8.0.0)
7=Direct assignmentRight to Left
+=  -=  *=  /=  %=  **=Compound assignment by addition, subtraction, multiplication, division, remainder, and exponentiation
.=  ??=Concatenating assignment operator, Null coalescing assignment operator
<<=  >>=Compound assignment by Bitwise left shift and right shift
&=  ^=  |=Compound assignment by Bitwise AND, XOR and OR
6yield fromyield fromNA
5yieldyield
4printprint
3andLogical ANDLeft to Right
2xorLogical XOR
1orLogical OR

❮ PHP - Operators

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