This is a very bad idea.
The resulting code is likely to have many issues in it that include
- Poorly documented code
- very hard to maintain and update
- Spaghetti code
- tangled mess of jumps and loops all over the code, very hard for someone to understand. even by the original coder a few days later!
- Duplication of code
- wasting memory and running speed
- Very hard to develop by more than one person
- there is only one file
- Very hard to debug
- it either works or it doesn't