To measure memory usage of a single PHP function call, use the memory_get_usage() and memory_get_peak_usage() functions. 1. Use memory_get_usage() to obtain the memory difference before and after function execution to calculate the actual increased memory usage; 2. Use memory_get_peak_usage() to obtain the maximum memory peak during function execution, including temporarily allocated memory; 3. For more in-depth analysis, enable Xdebug extension to generate performance analysis files, and combine tools such as KCacheGrind to view detailed memory and time consumption, but it should be noted that Xdebug is only applicable to development environments and should not be enabled in production environments.

To measure the memory usage of a single PHP function call, you can use built-in PHP functions like memory_get_usage() and memory_get_peak_usage() . These functions allow you to track how much memory your script is using at different points in time. The general idea is to take a memory snapshot before and after the function call to calculate the difference.

Use memory_get_usage() for basic tracking

This function returns the amount of memory, in bytes, that's currently being allocated to your PHP script. To get the memory used by a specific function, you'd typically do something like this:

 $startMemory = memory_get_usage();
yourFunctionHere();
$endMemory = memory_get_usage();

echo 'Memory used: ' . ($endMemory - $startMemory) . ' bytes';

• Make sure not to run other code between the two calls, or it will skew the result.
• This method gives you the increase in memory from the start to end of the function.
• It doesn't account for garbage collection or temporary spikes during execution.

Check peak memory with memory_get_peak_usage()

If you're interested in the maximum amount of memory used during the function's execution (including any temporary allocations), use memory_get_peak_usage() :

 $startPeak = memory_get_peak_usage();
yourFunctionHere();
$endPeak = memory_get_peak_usage();

echo 'Peak memory used: ' . ($endPeak - $startPeak) . ' bytes';

• This is useful when a function may allocate large temporary data structures that are later freed.
• Keep in mind that this value includes everything allocated during the function's run, not just what's retained afterward.

Consider enabling Xdebug for more detailed analysis

For deeper profiling — especially if your function calls other functions or uses complex logic — consider using Xdebug , a powerful PHP extension for debugging and profiling.

• Xdebug can generate cachegrind files that you can open in tools like KCacheGrind or WinCacheGrind to see exactly how much memory (and time) each function call takes.
• Enable it by setting xdebug.mode=profile in your php.ini and configure the output directory with xdebug.output_dir .
• Once enabled, calling your function via the web or CLI will generate a profile file showing full stack memory and timing details.

Just keep in mind:

• Xdebug adds overhead, so don't enable it on production servers.
• It's best suited for development and troubleshooting performance issues.

Basically that's it. Using a combination of built-in functions and profiling tools like Xdebug should give you a solid understanding of how much memory a specific PHP function consumes during its execution.

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