Memory

Memory refers to the portion of server RAM that PHP uses to execute scripts.

Whenever a PHP application runs, it needs memory to load the PHP engine, parse the code, store data and various caches.

Memory usage is controlled by the memory_limit directive, and functions like get_memory_usage().

PHP handles the memory management, and there is little more to do beyond setting the overall limit, although some features may become memory hungry easily, such as array_merge() in loops, or the N+1 query problem.

Related : memory_limit, Circular Reference, Free, Garbage Collection, Shared Memory, Treemap