bzcompress() compresses the source string and returns it as bzip2 encoded data.
The optional parameter blocksize specifies the blocksize used during compression and should be a number from 1 to 9 with 9 giving the best compression, but using more resources to do so. blocksize defaults to 4.
The optional parameter workfactor controls how the compression phase behaves when presented with worst case, highly repetitive, input data. The value can be between 0 and 250 with 0 being a special case and 30 being the default value. Regardless of the workfactor, the generated output is the same.