Question about useless variables

When I have useless not used variables in code 500+ can it slowdown my server?

 

Variables take up a small bit of the free memory. This does not necessarily mean the server becomes slower, but like t says, it does take up more memory, which could, in extreme amounts, cause potential crashes. *citation needed*

 

PHP would eventually perform a memory cleanup which would get rid of the unused vars.

 

I wonder if it actually possible to make so many variables that a server crashes. Interesting thing to find out.