How can PHP developers ensure proper handling of special characters like ö,ü,ä, or ß in form input fields to avoid issues with data storage and retrieval?

Special characters like ö,ü,ä, or ß can cause issues with data storage and retrieval if not properly handled in PHP. To ensure proper handling, PHP developers should use functions like htmlspecialchars() or htmlentities() to encode special characters before storing them in a database and decode them when retrieving the data.

// Encoding special characters before storing in the database
$input = $_POST['input_field'];
$encoded_input = htmlspecialchars($input, ENT_QUOTES);

// Storing the encoded input in the database

// Retrieving the encoded input from the database
$decoded_input = htmlspecialchars_decode($encoded_input);

// Displaying the decoded input
echo $decoded_input;