PHP 5.5 vs PHP 7 performance comparison for Moodle 3.0

Enovation Admin | Blog, News | 15 November, 2015

There is a lot of interesting things going on in the Moodle & PHP worlds recently – Moodle 3.0 has just been released and PHP 7 release is coming soon. Among other things, PHP 7 promises a great performance improvement over PHP 5.6 – PHP 7 is supposedly up to 2 x faster.

We have decided to put that into the test by simulating real-world Moodle 3.0 usage scenario. After a quick Moodle PHP 7 bug fix and hack to ignore Moodle version check, we were able to install Moodle using PHP 7.

The environment used for testing:

Moodle: 3.0rc4 (Build: 20151113)
PHP: Version 7.0.1-dev with Zend OPcache v7.0.6-dev vs PHP Version 5.5.9 with Zend OPcache v7.0.3 (Ubuntu 14.04 packaged version)
OS: 64 bit Ubuntu 14.04
Mysql server 5.5
Physical machine with:
- 16GB RAM
- one 2GHz i7-2630QM CPU (4 cores, 8 threads)
- SSD hard drive

The test was performed with jmeter running on the same machine. This has affected the performance of the system but it should be the same overhead for running both PHP versions, so it should not matter for the comparison. We have tested 200 users answering 100 quiz questions each. Each user had a separate account and started his run by login, followed by answering 100 questions and submitting the quiz. Every question was on a separate page, so each user generated over 200 page hits. The test was set up to run 20 threads in parallel. The timings are taken from jmeter statistics and from Moodle performance reporting (MDL_PERF). After switching PHP version we have run & discarded dozens of jmeter tests to warm up all caches. All tests were executed with opcache enabled.

The results are grouped by PHP script that was run and show:

the times it took to execute each PHP script (with minimum time, maximum, average and standard deviation) measured in seconds
values like above for CPU time (the time that CPU has spent working on each request) in seconds
memory used shown in MB

The most relevant values for a comparison like this are CPU time and memory used, so let’s see how well did PHP 7 do compared to PHP 5.

PHP 5.5 results

script	count	min_time	max_time	avg_time	std_time	min_cpu	max_cpu	avg_cpu	std_cpu	mem_min	mem_max	mem_avg	mem_std
/login/index.php	200	1.09	3.21	2.01	0.40	0.94	1.05	0.98	0.02	4.71	4.71	4.71	0.00
/mod/quiz/attempt.php	20200	0.20	1.68	0.80	0.18	0.19	0.49	0.43	0.01	10.84	11.01	10.94	0.03
/mod/quiz/processattempt.php	20199	0.06	2.23	0.45	0.16	0.06	0.73	0.23	0.05	10.10	11.71	10.16	0.15
/mod/quiz/review.php	200	0.28	1.57	0.96	0.27	0.26	0.49	0.45	0.04	11.52	11.56	11.54	0.01
/mod/quiz/startattempt.php	200	1.80	4.42	2.80	0.55	1.18	1.30	1.24	0.02	12.04	12.07	12.06	0.01
/mod/quiz/view.php	200	0.22	1.19	0.71	0.17	0.21	0.36	0.32	0.01	12.16	12.16	12.16	0.00

PHP 7 results

script	count	min_time	max_time	avg_time	std_time	min_cpu	max_cpu	avg_cpu	std_cpu	mem_min	mem_max	mem_avg	mem_std
/login/index.php	200	0.96	2.33	1.29	0.23	0.87	1.01	0.94	0.02	3.23	3.23	3.23	0.00
/mod/quiz/attempt.php	20200	0.04	0.72	0.24	0.07	0.04	0.31	0.18	0.02	7.31	7.43	7.38	0.02
/mod/quiz/processattempt.php	20198	0.03	1.27	0.15	0.06	0.02	0.32	0.09	0.02	6.04	7.50	6.09	0.14
/mod/quiz/review.php	200	0.08	0.57	0.30	0.08	0.05	0.22	0.20	0.02	7.74	7.76	7.74	0.00
/mod/quiz/startattempt.php	200	0.18	2.71	0.94	0.42	0.13	0.56	0.50	0.04	7.44	7.50	7.45	0.01
/mod/quiz/view.php	200	0.06	1.26	0.25	0.11	0.05	0.20	0.15	0.01	7.67	7.67	7.67	0.00

PHP 5.5 vs 7

The table below show how much % of time / memory was consumed by PHP 7 compared to PHP 5.5.

script	avg_cpu_time	avg_time	memory_avg
/login/index.php	96.03	64.22	68.55
/mod/quiz/attempt.php	41.96	30.57	67.45
/mod/quiz/processattempt.php	41.85	33.25	59.95
/mod/quiz/review.php	43.88	31.65	67.13
/mod/quiz/startattempt.php	39.92	33.57	61.75
/mod/quiz/view.php	45.69	35.14	63.06

In summary, PHP 7 performed more than 2 time faster compared to PHP 5.5 while consuming only 60% of the memory that PHP 5.5 did. Statistics from jMeter confirm that – PHP 5.5 was able to process on average 10 requests per second, while PHP 7 20 requests/second.

Keep in mind that the above does not mean that your users will get this kind of performance improvement as soon as you switch to new PHP version. The time measured here is a CPU time on the server side, which is just a fraction of the whole time needed to render the page for end user. Once you add network latency, loading media and rendering the page by the browser – the end result will be much less spectacular. Having said that the results are quite impressive – go PHP 7!