What are the potential pitfalls of using multiple databases in PHP applications?

Potential pitfalls of using multiple databases in PHP applications include increased complexity, potential for data inconsistency, and performance issues due to cross-database queries. To mitigate these risks, consider using a database abstraction layer or ORM framework to handle interactions with multiple databases in a unified manner. 

// Using a database abstraction layer example
$database1 = new Database('host1', 'username1', 'password1', 'database1');
$database2 = new Database('host2', 'username2', 'password2', 'database2');

// Query database 1
$result1 = $database1->query('SELECT * FROM table1');

// Query database 2
$result2 = $database2->query('SELECT * FROM table2');

Keywords

SQL injection database connection data consistency transaction management performance optimization

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