If you spend time around software engineers or businesspeople interested in building or running big systems, you’ll hear them ask questions like “Does this scale?” or “Is this system scalable?” They are not talking about cleaning fish. They are wondering, sometimes imprecisely, what happens when this system gets big and busy? Does the website that is speedy with 3 people using it get slow when 3,000 people are using it? What about 3,000,000 people?
The best advice about making a scalable system for a beginning programmer is “don’t worry about it for now.” It is far more important to get things (mostly) working at first with just a light burden on your application than it is to ensure up front that everything will be OK with a heavy burden.
What’s more, when you do start to notice performance issues in your application, your PHP code is probably not the biggest problem. Many things can affect an application’s performance. An inefficient database query that takes a few seconds to run makes a web page load very slowly, even if the PHP program sending the query to the database and generating HTML from the database’s response only takes a few milliseconds to do its part. A web page that the server quickly sends to a client still feels slow to a human user if the HTML loads hundreds of images that take a long time to display in a web browser.
When you do get to the point of ensuring that the PHP-specific parts of your application are speedy, use a profiler to gather data on how the PHP engine performs when running your code. The two most popular open source profilers are Xdebug and XHProf. XHProf has not been updated to work with PHP 7. Xdebug supports PHP 7 as of its 2.4.0rc1 release in November 2015.
As discussed in Chapter 12, Xdebug integrates with several IDEs, including PhpStorm and NetBeans. To learn about profiling in PhpStorm, read the JetBrains article about it. If you’re not using PhpStorm, check out the Xdebug docs for generic information on getting Xdebug’s profiler up and running and then viewing the profiling output.
Source: Sklar David (2016), Learning PHP: A Gentle Introduction to the Web’s Most Popular Language, O’Reilly Media; 1st edition.