PHP stands for “PHP: Hypertext Pre-processor.” It is an alternative to Microsoft's Active Server Pages (ASP).
I would suggest that you go through at least three different basic PHP on-line tutorials. Each writer has his/her own style and layout. Furthermore, each student has his/her own preference as to material and explanations. By going through three tutorials, you will have overlapping information that reinforces your knowledge and acquired expertise. In addition, some sites will have information that the others do not, or may explain somethings in a more understandable way.
I would also strongly recommend that you get a couple of ...For Dummies, ...Made Easy, Teach Yourself...in 21 Days books (from your local library or bookstore).
For on-line tutorials, you can google these three terms together:
PHP tutorial free
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Explore various sites, until you find three or four whose style, content, and setup are to your liking.
Here are three links:
http://www.freewebmasterhelp.com/tutorials/php
http://mgeisler.net/php-tutorial/
http://www.htmlgoodies.com/beyond/php/article.php/3472431
Good luck.