Thank you. I was going crazy trying to think of what the contents of that 42 bytes would have been.

Without any headers, metadata or padding and using RLE one byte for 0 and 8 bytes for the number of zeroes: 10^15 will easily fit 9 bytes and can be used to generate a file filled with one petabyte of zeroes.

Well, yes, but that's not ZIP encoding.

thanks I fixed it

Another small point, you don't need that starts with function, just use strpos === 0.

It's actually good practice to wrap a bit of code like that in a function with a name, as long as it isn't in some kind of extremely frequently executed inner loop.

'starts_with' is descriptive and language agnostic where '=== 0' is neither.