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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*. If operator precedence is equal, left to right associativity is used.

The following table lists the precedence of operators with the highest-precedence operators listed at the top of the table. Operators on the same line have equal precedence, in which case their associativity decides which order to evaluate them in.

Associativity | Operators | Additional Information |
---|---|---|

non-associative | clone new | clone and new |

left | [ | array() |

non-associative | ++ -- | increment/decrement |

right | ~ - (int) (float) (string) (array) (object) (bool) @ | types |

non-associative | instanceof | types |

right | ! | logical |

left | * / % | arithmetic |

left | + - . | arithmetic and string |

left | << >> | bitwise |

non-associative | < <= > >= <> | comparison |

non-associative | == != === !== | comparison |

left | & | bitwise and 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 |

Left associativity means that the expression is evaluated from left to right, right associativity means the opposite.

**Example #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

?>

Note:Although

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