How can variable naming conventions impact the readability and maintenance of PHP code?

Variable naming conventions can impact the readability and maintenance of PHP code by making it easier for developers to understand the purpose of each variable. Consistent and descriptive variable names can make the code more self-documenting and reduce the need for additional comments. By following a naming convention, such as using camelCase or snake_case, developers can quickly identify the type and purpose of each variable, which can improve code readability and make it easier to maintain in the long run.

// Bad variable naming convention
$userid = 1;
$username = "John";

// Good variable naming convention
$user_id = 1;
$user_name = "John";