The php_generated.txt file was generated by running parse_types.py on the source code of php.
Possible improvements:
<fuzzfunction> always point to phpinfo). Generating callback code in a similar manner to the main function could potentially expose additional bugs, especially if callbacks get access to the same variables / can mess up stuff that the caller didn't expect.parse_type.py code is ugly, and should be refactored a bit.$ref_ in template.php).