Is there a limit to the filesize of the *.pmp file?
It appears to me that when I add some custom pages, which can substantially increase the project filesize, I can't exceed 21,000 lines of XML in the PMP file. Content after that is truncated when saved.
There is no such limit, but a large file will make the UI slow. If you add a Custom File, the file content is stored in the project file. If your file content is large or you have a lot of Custom Files, the project size will become large. As explained in the help file, in such cases you should not store the file content in the project, you can use include files, for example.
My project file exceeds 71,000 lines of code without an issue. As the webmaster suggests, I also use "include" files whenever possible.
Following up: I found that the PHP command ob_get_clean is where my custom page choked my project. Perhaps there are some PHP commands that choke PHPMaker. Creating such a PHP document outside of PHPMaker is the only solution. My intention was to keep everything within PHPMaker, including custom pages. But this limitation prevents that. Minor thing, really. Thank you to all who offered assistance.
Project file is just a XML file, no PHP command could possibly prevent it from saving your code because they are just text. In addition, all code for a custom file is stored in CDATA of XML file. So there is NO such limitation. The only possible cause might be that you might have copied and pasted some non-unicode characters from somewhere else so that it cannot be saved in the utf-8 encoded project file. You can rename the project file as .xml file and then open it in browser to check the well-formedness of the XML file.