The parameter block is the fundamental data structure within the server code. The parameter block, or pblock, is a hash table keyed on the name string, which maps these name strings onto their value character strings.
For more information about the parameter block, see pblock Data Structure.
All server application functions have the following syntax:
int function(pblock *pb, Session *sn, Request *rq);
Where, pb is the parameter block with the parameters given by the site administrator for this function invocation. This parameter should be considered read-only, and any data modification should be performed on copies of the data. Doing otherwise is unsafe in threaded server architectures, and yields unpredictable results in multi-process server architectures.