What is the potential issue with using "echo" instead of "return" in PHP functions?

Using "echo" instead of "return" in PHP functions can cause unexpected behavior, as "echo" outputs the result directly to the browser rather than returning it for further processing. To solve this issue, you should use "return" to pass the value back to the calling code. This allows you to capture the result and use it as needed, instead of immediately displaying it on the screen.

function addNumbers($num1, $num2) {
    $sum = $num1 + $num2;
    return $sum;
}

$result = addNumbers(5, 3);
echo $result; // Output: 8