What are some best practices for handling variables in PHP?

When handling variables in PHP, it is important to properly sanitize user input to prevent security vulnerabilities such as SQL injection or cross-site scripting attacks. One common best practice is to use PHP's built-in functions like filter_var() or htmlentities() to sanitize input data before using it in your code. 

// Example of sanitizing user input using filter_var()
$user_input = $_POST['user_input'];
$sanitized_input = filter_var($user_input, FILTER_SANITIZE_STRING);
```

Another best practice is to always validate and sanitize data before using it in SQL queries to prevent SQL injection attacks.

```php
// Example of sanitizing user input for SQL queries
$user_input = $_POST['user_input'];
$sanitized_input = mysqli_real_escape_string($connection, $user_input);
$query = "SELECT * FROM users WHERE username = '$sanitized_input'";
$result = mysqli_query($connection, $query);

Keywords

variable scope data sanitization type coercion error handling constant variables

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