How can PHP code be modified to prevent duplicate entries in a database when a form is submitted multiple times?

To prevent duplicate entries in a database when a form is submitted multiple times, you can check if the entry already exists in the database before inserting a new record. This can be done by querying the database with the input data to see if a matching record already exists. If a matching record is found, you can display an error message to the user instead of inserting a duplicate entry. 

// Assuming $conn is the database connection

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $input_data = $_POST['input_data'];
    
    // Check if the entry already exists in the database
    $query = "SELECT * FROM your_table WHERE column_name = '$input_data'";
    $result = mysqli_query($conn, $query);
    
    if (mysqli_num_rows($result) > 0) {
        echo "Entry already exists in the database.";
    } else {
        // Insert the new record into the database
        $insert_query = "INSERT INTO your_table (column_name) VALUES ('$input_data')";
        mysqli_query($conn, $insert_query);
        echo "Record inserted successfully.";
    }
}

Keywords

PHP database duplicate entries form submission prevention

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