Learning PHP through a book entitled Beginning PHP and MySQL 5: From Novice to Professional, Second Edition by W. Jason Gilmore.
PHP is a loosely-typed language due to its origin as a web counter script. This is inherent in the quick and dirty way it does things, one can put in a variable and assign and reassign it to various data types like strings, integers and floats. There is no need for declarations and type-casting, though it is available. Coming from a Java background, that is very off-putting. Acclimation would be easy but care must be taken to prevent any bad programming habits from creeping in.
The OOP aspect of PHP is a mix of C and Java coding styles. In that respect, it is pretty conventional and a Java programmer can take easily to it. Relatively simple websites should be easy to prototype quickly.