What are the best practices for naming variables and functions in PHP to avoid errors?

When naming variables and functions in PHP, it is important to follow certain best practices to avoid errors. Variable and function names should be descriptive, meaningful, and follow a consistent naming convention such as camelCase or snake_case. Avoid using reserved keywords, special characters, or starting variable names with numbers. By following these best practices, you can improve code readability and reduce the likelihood of errors.

// Example of naming variables and functions following best practices
$firstName = "John";
$lastName = "Doe";

function calculateTotal($price, $quantity) {
    return $price * $quantity;
}