What are the best practices for handling form data validation and submission in PHP to prevent errors like undefined index?

When handling form data in PHP, it is important to validate the input and ensure that the necessary fields are set before processing the data to prevent errors like "undefined index." One way to prevent this error is to check if the form fields are set using the isset() function before accessing them in the $_POST array. 

if(isset($_POST['submit'])){
    $name = isset($_POST['name']) ? $_POST['name'] : '';
    $email = isset($_POST['email']) ? $_POST['email'] : '';
    
    // Process the form data here
}

Keywords

$_POST isset() empty() filter_input() error_reporting(E_ALL)

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