What are some common pitfalls when writing complex PHP-MySQL scripts?

One common pitfall when writing complex PHP-MySQL scripts is not properly sanitizing user input, leaving the script vulnerable to SQL injection attacks. To solve this issue, always use prepared statements or parameterized queries to safely execute SQL queries with user input. 

// Example of using prepared statements to prevent SQL injection
$stmt = $pdo->prepare("SELECT * FROM users WHERE username = :username");
$stmt->bindParam(':username', $username);
$stmt->execute();
```

Another common pitfall is not properly handling errors and exceptions when interacting with the database. To address this, always use try-catch blocks to catch any potential errors that may arise during database operations.

```php
// Example of using try-catch blocks to handle errors when interacting with the database
try {
    $pdo = new PDO("mysql:host=localhost;dbname=mydatabase", "username", "password");
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}
```

Lastly, another pitfall is not optimizing database queries, leading to slow performance. To improve performance, make sure to index columns used in WHERE clauses, limit the number of rows returned, and avoid unnecessary JOIN operations.

```php
// Example of optimizing a database query by limiting the number of rows returned
$stmt = $pdo->prepare("SELECT * FROM users LIMIT 10");
$stmt->execute();

Keywords

MySQL PHP SQL injection performance optimization error handling

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