Does PHP have short-circuit evaluation?

Yes, the PHP interpreter is "lazy", meaning it will do the minimum number of comparisons possible to evaluate conditions.

If you want to verify that, try this:

function saySomething(){    echo 'hi!';    return true;}if (false && saySomething()){    echo 'statement evaluated to true';}

Yes, it does. Here's a little trick that relies on short-circuit evaluation. Sometimes you might have a small if statement that you'd prefer to write as a ternary, e.g.:

    if ($confirmed) {        $answer = 'Yes';    } else {        $answer = 'No';    }

Can be re-written as:

   $answer = $confirmed ? 'Yes' : 'No';

But then what if the yes block also required some function to be run?

    if ($confirmed) {        do_something();        $answer = 'Yes';    } else {        $answer = 'No';    }

Well, rewriting as ternary is still possible, because of short-circuit evaluation:

    $answer = $confirmed && (do_something() || true) ? 'Yes' : 'No';

In this case the expression (do_something() || true) does nothing to alter the overall outcome of the ternary, but ensures that the ternary condition stays true, ignoring the return value of do_something().

Bitwise operators are & and |.They always evaluate both operands.

Logical operators are AND, OR, &&, and ||.

• All four operators only evaluate the right side if they need to.
• AND and OR have lower precedence than && and ||. See example below.

From the PHP manual:

// The result of the expression (false || true) is assigned to $e// Acts like: ($e = (false || true))$e = false || true;// The constant false is assigned to $f before the "or" operation occurs// Acts like: (($f = false) or true)$f = false or true;

In this example, e will be true and f will be false.