With so many new features, especially related to improved OO support, it's almost impossible that every PHP 4 script will continue to work with PHP 5. The PHP development team tried to make migrating to PHP 5 as painless as possible, but you can encounter some minor incompatibilities. This chapter covers things that might break when you run your PHP 4 scripts on PHP 5 and how to change the scripts.
When you finish reading this chapter, you will have learned
How to revert some PHP 5 behavior to PHP 4 behavior with a php.ini setting
Recognize other compatibility problems in scripts using OO features
The new names and locations of files in the PHP 5 distribution
How to use some functions that have changed