Operators
Arithmetic Operators
Operators
PHP Manual

## Operator Precedence

The precedence of an operator specifies how "tightly" it binds two expressions together. For example, in the expression 1 + 5 * 3, the answer is 16 and not 18 because the multiplication ("*") operator has a higher precedence than the addition ("+") operator. Parentheses may be used to force precedence, if necessary. For instance: (1 + 5) * 3 evaluates to 18.

When operators have equal precedence, their associativity decides whether they are evaluated starting from the right, or starting from the left - see the examples below.

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 the order of evaluation.

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

For operators of equal precedence, left associativity means that evaluation proceeds from left to right, and right associativity means the opposite.

Przykład #1 Associativity

`<?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
// mixing ++ and + produces undefined behavior
$a = 1;
echo ++$a + $a++; // may print 4 or 5
?>`
Use of parentheses, even when not strictly necessary, can often increase readability of the code.

> Informacja:

> Although = has a lower precedence than most other operators, PHP will still allow expressions similar to the following: if (!$a = foo()), in which case the return value of foo() is put into $a.

Operators
Arithmetic Operators
Operators
PHP Manual