Chapter 10. Operators
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.
The following table lists the precedence of operators with the lowest-precedence operators listed first.
Table 10-1. Operator Precedence
| Associativity | Operators |
|---|---|
| left | , |
| left | or |
| left | xor |
| left | and |
| right | |
| right | = += -= *= /= .= %= &= |= ^= <<= >>= |
| left | ? : |
| left | || |
| left | && |
| left | | |
| left | ^ |
| left | & |
| non-associative | == != === !== |
| non-associative | < <= > >= |
| left | << >> |
| left | + - . |
| left | * / % |
| right | ! ~ ++ -- (int) (float) (string) (array) (object) @ |
| right | [ |
| non-associative | new |
Note: Although ! has a higher precedence than =, PHP will still allow expressions similar to the following: if (!$a = foo()), in which case the output from foo() is put into $a.