PHP 7 Programming Cookbook

Embedding secondary lookups into query results

On the road towards implementing relationships between entity classes, let us first take a look at how we can embed the code needed to perform a secondary lookup. An example of such a lookup is when displaying information on a customer, have the view logic perform a second lookup that gets a list of purchases for that customer.

Note

The advantage of this approach is that processing is deferred until the actual view logic is executed. This will ultimately smooth the performance curve, with the workload distributed more evenly between the initial query for customer information, and the later query for purchase information. Another benefit is that a massive JOIN is avoided with its inherent redundant data. ...