In what situations should PHP developers consider using isset() or !empty() instead of <> or != when checking user input?

When checking user input in PHP, developers should consider using isset() or !empty() instead of <> or != when they want to specifically check if a variable is set and not empty. This is important because using <> or != can lead to unexpected results, especially when dealing with user input that may be null or empty. By using isset() or !empty(), developers can accurately determine if a variable has been set and contains a value.

// Using isset() to check if a variable is set and not empty
if(isset($_POST['input']) && !empty($_POST['input'])){
    // Process the input
    $input = $_POST['input'];
    echo "User input: " . $input;
} else {
    echo "Input is not set or empty";
}