PHP is a great language to start out with. If you are looking for a solid PHP book recomendation it would depend on which version of PHP you want to learn. There is PHP4 which is still in use on most web servers, then there is the new PHP5 (i suggest if you know nothing at all you start with PHP5) This may seem like a bad suggestion at first because there are not a lot of web hosts that support it yet, however by the time you get through the in's and out's of the learning curve then by that time i think they will be widely available.
I can suggest a few books on PHP5 that i have in my library and find useful.
Core PHP Programming
MySQL / PHP Database Applications
Also keep in mind you will want a good database book too since PHP works closely with databases. You can choose whichever database you want to use. Some examples are Sqlite, MySQL, Postgre SQL, Microsoft Access, MS SQL Server I personally use MySQL and have the following book.
SQL The Complete Reference
Now as previously stated, you dont need to buy any books to learn the basics of PHP, that is if you can understand the manual (90% of people can) http://www.php.net/docs/
I know what i said above you may not understand it all however google for things such as design patterns, regular expressions etc.. and learn about them ;)
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