I'm learning PHP and noticed that `||` and `or` both seem to represent logical OR. I also found that `` and `!=` appear to mean "not equal." Are these pairs fully interchangeable, or are there differences I should know about? Search results haven't been very clear, especially regarding how these operators behave in larger expressions.
2 Answers
In simple conditions, `||` and `or` both perform a logical OR, but they do not have the same operator precedence. `||` has higher precedence than assignment, while `or` has lower precedence. That means these can behave differently: `$result = true || false;` assigns the result of the OR expression to `$result`, while `$result = true or false;` effectively evaluates the assignment first, leaving `$result` as `true`. For conditions, `||` is usually the less surprising choice; if you use `or`, add parentheses when the intended grouping matters.
Yes, `` and `!=` are equivalent in PHP: both mean “not equal.” The important distinction is between the two OR operators, since `||` and `or` differ in precedence even though they represent the same logical operation.
A clearer example is `$result = false || true;`, since `||` is evaluated before the assignment and `$result` becomes `true`.