What are some common methods for handling form submissions in PHP to avoid duplicate data entries?

To avoid duplicate data entries when handling form submissions in PHP, one common method is to check if the submitted data already exists in the database before inserting it. This can be done by querying the database with the submitted data to see if a matching record already exists. If a match is found, the form submission can be rejected to prevent duplicate entries. 

// Connect to the database
$connection = new mysqli('localhost', 'username', 'password', 'database');

// Check if the form was submitted
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $submittedData = $_POST['data'];

    // Check if the submitted data already exists in the database
    $query = "SELECT * FROM table WHERE data = '$submittedData'";
    $result = $connection->query($query);

    if ($result->num_rows > 0) {
        echo "Duplicate entry found. Please try again.";
    } else {
        // Insert the data into the database
        $insertQuery = "INSERT INTO table (data) VALUES ('$submittedData')";
        $connection->query($insertQuery);
        echo "Data submitted successfully.";
    }
}

Keywords

form submissions PHP duplicate data handling entries

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