Returns the peak of memory allocated by PHP - Справочник: PHP5.4

int memory_get_peak_usage ([ bool $real_usage = false ] )

Returns the peak of memory, in bytes, that's been allocated to your PHP script.

real_usage: Set this to TRUE to get the real size of memory allocated from system. If not set or FALSE only the memory used by emalloc() is reported.

Returns the memory peak in bytes.

Версия	Описание
5.2.1	Compiling with --enable-memory-limit is no longer required for this function to exist.
5.2.0	`real_usage` was added.