How can PHP be used 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 form data to see if a matching entry already exists. If a matching entry is found, you can display an error message to the user instead of inserting a duplicate record. 

// Assuming $conn is the database connection object and $formData is an array containing form data

// Check if the entry already exists in the database
$query = "SELECT * FROM your_table WHERE column_name = :value";
$stmt = $conn->prepare($query);
$stmt->bindParam(':value', $formData['value']);
$stmt->execute();

if ($stmt->rowCount() > 0) {
    // Entry already exists, display an error message
    echo "Entry already exists in the database.";
} else {
    // Insert the new record into the database
    $insertQuery = "INSERT INTO your_table (column_name) VALUES (:value)";
    $insertStmt = $conn->prepare($insertQuery);
    $insertStmt->bindParam(':value', $formData['value']);
    $insertStmt->execute();
}

Keywords

PHP database duplicate entries form submission validation

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