What potential pitfalls should beginners be aware of when working with PHP, especially when creating complex class structures like in the example provided?

One potential pitfall beginners should be aware of when working with PHP, especially when creating complex class structures, is the risk of circular dependencies. This occurs when two or more classes depend on each other, causing a deadlock situation. To avoid this issue, it's important to carefully plan and organize the class relationships to prevent circular dependencies. 

// Example of avoiding circular dependencies by using interfaces

interface DatabaseInterface {
    public function connect();
    public function query($sql);
}

class MySQLDatabase implements DatabaseInterface {
    public function connect() {
        // Connect to MySQL database
    }

    public function query($sql) {
        // Execute query on MySQL database
    }
}

class UserRepository {
    private $db;

    public function __construct(DatabaseInterface $db) {
        $this->db = $db;
    }

    public function getUsers() {
        // Use $this->db to fetch users from database
    }
}

Keywords

Inheritance Namespace Autoloading Dependency Injection Magic Methods

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