The purpose of this extension is to detect the most memory hungry scripts and functions.
memtrack tracks memory consumption in PHP scripts and produces reports (warnings) when the consumption reaches certain levels set by the user. This is achieved by replacing default executor function by a special function which compares memory usage before and after running the original executor - this way we can tell how much the memory usage has changed during the execution of the current part of the code.
Zend Engine runs its executor for each opcode array (op_array), which usually means function, plain script and such, so memtrack doesn't have any noticeable effect on performance.
memtrack doesn't provide any functions, there are only INI directives which allow you to configure the way it should work.
This extension is EXPERIMENTAL. The behaviour of this extension including the names of its functions and any other documentation surrounding this extension may change without notice in a future release of PHP. This extension should be used at your own risk.