What are common issues that can arise when using PHP for form submissions and database interactions?

Issue: SQL Injection To prevent SQL injection attacks, always use prepared statements with bound parameters when interacting with a database in PHP. 

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

Issue: Cross-Site Scripting (XSS)
To prevent XSS attacks, always sanitize user input before displaying it on a webpage in PHP.

```php
// Example of sanitizing user input to prevent XSS
echo htmlspecialchars($user_input);
```

Issue: Form Validation
Always validate user input on the server-side to ensure data integrity and security.

```php
// Example of form validation in PHP
if (isset($_POST['submit'])) {
    $username = $_POST['username'];
    
    // Validate username
    if (empty($username)) {
        echo "Username is required";
    } else {
        // Process form submission
    }
}

Keywords

SQL injection XSS attacks form validation PDO prepared statements

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