PDF doesn't encode something. PDF supports a few data formats. They call them "filters"; for example CCITT Fax, JBIG2, DCT, RLE, etc. Its up to the PDF creation program to pick the best data format for the image it would like to put into the PDF.
398 karma · joined June 19, 2013
I'm not saying PHP executes just like Java, but PHP is more like Java than he realizes. PHP does not execute line by line like an interpreted language. But takes the source and compiles it down to an intermediate representation (IR), just like Java. Java calls it bytecode, PHP calls it OPCodes. Also like Java, PHP then takes that IR and executes it on a VM. Java's is stack based and PHP is register based, if I remember correctly. Many PHP accelerators / caching solutions save the IR and thus, the next time the code is needed, no compilation of source code is done.
1. https://xmlgraphics.apache.org/fop/ 2. https://www.princexml.com/