I have built the PHP language bindings with no errors, but when I run I get the following error.
Call to undefined function PDFNet_Initialize() … in …/PDFNetWrappers/PDFNetC/Lib/PDFNetPHP_core.php:18707
It appears your PHP did not load the libPDFNetC.so shared library.
The fix is to
enable_dl = On in your php.ini files, for example the two below.
You might also need to add the .so explicitly, or at least put the .so in a folder that PHP will load .so files from. See your PHP documentation.