Operator Precedence¶
The operator precedence dictates in which order the operators in a same sequence are executed.
For example, in the code 1 + 2 * 3, the order is the mathematical order: multiplication has precedence over addition. The results is 7, not 9.
In PHP, operators have different precedence: ., dot, has a lower priority than addition + and -.
Precedence may lead to unexpected behavior. For example, -9 ** 2 == -9, because - has lower precedence than **, and PHP doesn’t parse negative numbers in one pass.
Also, $a = $b & $c; means that $a = $b;, because = has a higher priority than &.
<?php
// 7, not 9
$a = 1 + 2 * 3;
// 11
$a = 4 * 2 + 3;
// equivalent to !($a instanceof aClass)
// ! has lower precedence than instanceof
$b = !$a instanceof aClass;
?>
See also Understanding the PHP Operator Precedence and Which Operators Come First?.
Related : Operators
