How can variable naming conventions impact code readability and maintainability in PHP?

Variable naming conventions impact code readability and maintainability by making it easier for developers to understand the purpose and usage of variables within the codebase. Consistent and descriptive variable names can help reduce confusion and errors when working on a project, especially in larger codebases or when collaborating with other developers. By following a naming convention, such as using camelCase or snake_case, developers can quickly identify the purpose of a variable and make changes or updates more efficiently.

// Example of using camelCase variable naming convention
$firstName = "John";
$lastName = "Doe";

// Example of using snake_case variable naming convention
$user_id = 123;
$user_name = "johndoe";