Rule

The use of literal logical operators (and, or) is discouraged. && and || should be used instead.

Reason

Operator precedence is different for and vs. && and or vs. ||.
It may cause unexpected behaviour:

$x = false || true;  // is ($x = (false || true)) => true
$x = false or true;  // is (($x = false) or true) => false
    
$x = true && false;  // is ($x = (true && false)) => false
$x = true and false; // is (($x = true) and false) => true

Please use the official documentation for more details.

Implementation

Add Squiz.Operators.ValidLogicalOperators to the ruleset.xml.