Common PHP directives influence how much data and processing time a PHP request can use.
memory_limitlimits memory available to a PHP request.upload_max_filesizelimits an individual PHP file upload.post_max_sizelimits the overall size of POST request data and generally needs to be at least as large as the intended upload.max_execution_timelimits script execution time in configurations where the directive applies.
Raising limits does not fix inefficient code and may increase resource usage. Adjust only what the application needs and remain within any server-level limits that the account cannot override.