Question

Can any body give me a a introduction of how to program efficiently minimizing memory usage in PHP program correctly and generate my program results using minimum memory ?

Answer 1

Based on how I read your question, I think you may be barking up the wrong tree with PHP. It was never designed for a low memory overhead.

If you just want to be as efficient as possible, then look at the other answers. Remember that every single variable costs a fair bit of memory, so use only what you have to, and let the garbage collector work. Make sure that you only declare variables in a local scope so they can get GC’d when the program leaves that scope. Objects will be more expensive than scalar variables. But the biggest common abuse I see are multiple copies of data. If you have a large array, operate directly on it rather than copying it (It may be less CPU efficient, but it should be more memory efficient).

If you are looking to run it in a low memory environment, I’d suggest finding a different language to use. PHP is nice because it manages everything for you (with respect to variables). But that type coersion and flexibility comes at a price (speed and memory usage). Each variable requires a lot of meta-data stored with it. So an 8 byte int (32 bit) would take 8 bytes to store in C, it will likely take more than 64 bytes in PHP (because of all of the “tracking” information associated with it such as type, name, scoping information, etc). That overhead is normally seen as ok since PHP was not designed for large memory loads. So it’s a trade-off. More memory used for easier programming. But if you have tight memory constraints, I’d suggest moving to a different language…