This tutorial targets the PHP developer who already understands PHP, but wants to write more efficient PHP code or to improve the performance of existing PHP applications. It is not intended as an introduction to PHP -- plenty of other resources are available for that. Rather, it assumes that you already have an installation of PHP available and are familiar with the basic PHP syntax. ...

In this tutorial, you will learn ways to improve the performance of your PHP code. The tutorial is in four main parts:

• General coding considerations that can be often applied to any language, but are illustrated with specific PHP examples.
• Nuances of the PHP language and how you can use them to further improve the efficiency of your PHP code.
• Improving the performance of your SQL queries since, for larger applications, PHP often is used in conjunction with a database.
• Making your PHP code run faster and references for further reading

You can read through this tutorial from beginning to end and pick up a wide variety of tips and advice on how to improve your PHP code without having anything in particular installed.

For the most value, you may want to construct and run some of your own test cases. To do this, you will need a working installation of PHP on your machine.
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Source: www.stevengould.org