There are many documentation websites that very concisely explain PHP's syntax. PHP.net is the official resource/language manual. W3Schools.com is also a reputable source for various documentation and tutorials.
There is no such thing as an official, beginner-friendly "cheat sheet" that concisely explains how to program PHP in one page, however. The language is much more complex than could be covered by very simple PDF cheat sheets such as these. My recommendation is to follow the W3schools tutorials and to use the official documentation to supplement where needed. This will give you a much deeper and more thorough understanding of the language and how it interacts with your browser.
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