What best practices should be followed when handling user input validation in PHP to prevent errors like duplicate entries in the database?

To prevent errors like duplicate entries in the database, it is important to perform proper user input validation in PHP. This can be achieved by checking if the input data already exists in the database before inserting it. Additionally, utilizing unique constraints in the database schema can help enforce data integrity and prevent duplicate entries. 

// Example code snippet for handling user input validation to prevent duplicate entries in the database

// Assume $inputData contains the user input data

// Check if the input data already exists in the database
$query = "SELECT COUNT(*) FROM table_name WHERE column_name = :inputData";
$stmt = $pdo->prepare($query);
$stmt->bindParam(':inputData', $inputData);
$stmt->execute();
$count = $stmt->fetchColumn();

if ($count > 0) {
    // Handle duplicate entry error
    echo "Error: Duplicate entry found in the database.";
} else {
    // Proceed with inserting the data into the database
    $insertQuery = "INSERT INTO table_name (column_name) VALUES (:inputData)";
    $insertStmt = $pdo->prepare($insertQuery);
    $insertStmt->bindParam(':inputData', $inputData);
    $insertStmt->execute();
    echo "Data inserted successfully.";
}

Keywords

SQL injection prepared statements data sanitization input filtering validation logic

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