What is the limitation of using empty() on expressions in PHP?

The limitation of using empty() on expressions in PHP is that it can only be used on variables and not on expressions that return a value. To work around this limitation, you can assign the expression to a variable and then use empty() on that variable instead.

// Example of using empty() on an expression
$value = 10 * 5;
// This will result in a syntax error
if (empty(10 * 5)) {
    echo "Expression is empty";
}

// Fix: Assign the expression to a variable and use empty() on the variable
$result = 10 * 5;
if (empty($result)) {
    echo "Expression is empty";
}