Watch out for the difference of priority between 'and vs &&' or '|| vs or':<?php$bool = true && false;var_dump($bool); // false, that's expected$bool = true and false;var_dump($bool); // true, ouch!?>Because 'and/or' have lower priority than '=' but '||/&&' have higher.

If you've come here looking for a full list of PHP operators, take note that the table here is *not* complete. There are some additional operators (or operator-ish punctuation tokens) that are not included here, such as "->", "::", and "...".For a really comprehensive list, take a look at the "List of Parser Tokens" page: http://php.net/manual/en/tokens.php

Note that ?? has a low priority, so this can lead to unexpected results:$a=[];$a['aa']??'not set' --> not set (as expected)but"lets see if it is set".$a['aa']??'not set'--> notice; undefined index aa--> lets see if it is setso you need to use parenthesis"lets see if it is set".($a['aa']??'not set')

Beware the unusual order of bit-wise operators and comparison operators, this has often lead to bugs in my experience. For instance:<?php if ( $flags & MASK  == 1) do_something(); ?>will not do what you might expect from other languages. Use<?php if (($flags & MASK) == 1) do_something(); ?>in PHP instead.

An easy trick to get the result of the left shift operation (<<), e.g.15 << 2 = 15 * (2*2) = 6015 << 3 = 15 * (2*2*2) = 12015 << 5 = 15 * (2*2*2*2*2) = 480and so on...So it's:(number on left) multiplied by (number on right) times 2.The same goes for the right shift operator (>>), where:(number on left) divided by (number on right) times 2 e.g.15 >> 2 = (15/2)/2 = 7/2 = 3 (use floor values if result is in decimals).35 >> 3 = (((35/2)/2)/2 = (17/2)/2 = 8/2 = 4

Using cast and ternary operator can be unclear,(Useful to know with: declare(strict_types = 1) ). <?php$num_str="5";$i1 = (int)  isset($num_str) ? $num_str : 0;$i2 = (int) (isset($num_str) ? $num_str : 0);var_dump($i1);var_dump($i2);?>Output:string(1) "5"int(5)

<?php // Another tricky thing here is using && or || with ternary ?:$x && $y ? $a : $b;  // ($x && $y) ? $a : $b;// while:$x and $y ? $a : $b;  // $x and ($y ? $a : $b);?>

//incorrect$a = true ? 0 : true ? 1 : 2; // (true ? 0 : true) ? 1 : 2 = 2//Unparenthesized `a ? b : c ? d : e` is not supported. Use either `(a ? b : c) ? d : e` or `a ? b : (c ? d : e)` //correct$a = (true ? 0 : true) ? 1 : 2; // (true ? 0 : true) ? 1 : 2 = 2==> correction documentation.