The PHP code can be redistributed in source or binary form provided that the terms of the PHP license are respected (see version 3.01).
In plain English, this means that you have to include the full license text in human-readable form with every distributed copy of PHP, whether source or binary. One way of doing this is to put a copy of the PHP license into a text file that you include with the source or binary package before distribution. This ensures that the license information can be read properly even when a binary is shipped. A text file containing license and copyright information is sometimes given the filename "Notices", and may be referred to as a "Notices file".
Some files in the PHP codebase have been contributed under other licenses. If you want to distribute these files, you also need to respect the terms of those licenses. To check, look for the terms indicated in the license + copyright comment block at the top of the source file.
The license terms for such a file may require that its own license and copyright information must be included with every distributed copy (including binaries). This is quite a common requirement, which can be satisfied by adding the appropriate license text into a text file for distribution purposes, like the "Notices"-type of file suggested above.
A single "Notices" file could be used to hold the collection of license and copyright information that applies to PHP in general (the PHP license) and any files with additional licenses that you want to distribute (for example Zend, TSRM etc.) It is good practice to indicate which source file(s) a particular license applies to.
You can distribute your own software product which has been derived from PHP, in source or binary form, provided that: