This document discusses various PHP optimization techniques based on tests and experience. It finds: - "echo" is 10-15% faster than "print" for comma separated output. - "isset()" and "empty()" are nearly identical, while "is_array()" is twice as slow. - String quotes have negligible performance differences. - Loop types like "for" and "while" only have small speed differences not impacting applications. - Using opcode caching can improve performance by 200-700% by eliminating script compilation overhead. APC is recommended.

1. PHP optimization
based on many information found on the internet and on
personal experience
by Fabrizio Parrella

2. How where the tests performed
Those tests have been made and repeated multiple
times then the values have been averaged and
the outliers removed. Your script/server might
give you different results, this might be because
your CPU/memory/internal process/PHP Garbage
Collector/etc... might interfere

3. String Output
Is there a difference between “echo” and “print” ?
“echo” and “print” serve the same exact purpose.
Various tests show that “echo” is about 10-15%
faster when using comma separated items.

4. Variable Type Checking
isset() vs. empty() vs is_array()
Often we need to check if a variable is set, so what
is the faster ?
isset() and empty() are pretty much identical
is_array() takes twice as long

5. Quotes
“ vs. '
Lots of information on the web about quotes.. which
is faster ?
In the past there were some minor performance
differences between “ and ' for a string that
doesn't contain variables.
In today's versions of PHP looks like that the
argument has been satisfied on both sides as
they are pretty much the same

6. Counting Loops
for vs. while
While or For.. For or While ? Many tests have been
done and many results have been posted all over
the internet.
In reality, there is not enough difference in execution
to make any very impact in the execution of the
application.
Micro-optimizing ?
The “while” is about 13% faster on an empty loop
that counts up to 1,000,000

7. Read Loops
foreach vs. for vs. while(list() = each())
This test is very tested like the “Counting Loops”
and there are various results around.
In my experience and the most commonly results
from other tests is that “foreach()” without $key is
the winner. The next closest is the “for()” and the
last is the “while()”.
If you must use the “while()” do not forget to use “reset()” first to
incredibly speed up the process.
“reset()” is good to use anytime you do a loop to reposition the pointer to the beginning

8. Control Structures
switch/case/default vs. if/elseif/else
There is no real difference between “switch” and “if”
There is a difference is the equality sign, where ===
is about 10% faster than ==

9. Counting Loops
For-Loop tests – calculate size in advance
Unsurprising results, calculate the size of the loop
ahead of time for a 1000x repetitions is incredibly
faster:
test time
Pre-calc - count() 243µs
No pre-calc - count() 109,472µs
Pre-calc - sifeOf() 200µs
No pre-calc - sizeOf() 104,085µs

10. Modify Loop
foreach() vs. for vs. while(list() = each())
Often happens that you need to modify the array
while you are looping it, when doing so it is best
not to loop the the array while modifying it
test time
foreach($array as $k=>$v) $array[$k] = 'value'; 362µs
while(list($k) = each($array)) $array[$k] = ''value'; 165µs
$ks = array_keys($array);
$size = count($k);
for($i=0; $i<=$size; $i++) $array[$ks[$i]] = 'value';
72µs

11. Got Perfect Code ?
so you wrote perfect code, but you want it to go faster
Have you ever heard of OPCODE caching?

12. What is OPCODE caching?
When a PHP script is called by a user:
●
User Requests the Page
●
Web Server Compiles the PHP script (interprets)
●
Executes the Compiled Version of the Page
●
Output the Data
Normal Applications do not need to be compiled as they are often pre-compiled,
however scripting languages like PHP, Perl, Ruby, etc., are compiled on demand
and interpreted. (there is a difference between compiling and interpreting, but that
is for another time).
As you can imagine, converting source code into machine code (opcode) can be
resource intensive. Opcode caches will store opcode in a cache and execute is
from there instead than constantly recompiling the code. This basically eliminate
the second step and seriously speed up the site.

13. It is Worth ?
You know what it is.. but is it worth to spend time installing it ?
Online research showed me that websites had
improvements between 200% and 700%.
My personal experience showed me a time saving
of 120%.
For example a page that before OPCode caching
took 10 µs to load, with APC installed it took 4µs.

14. The Best OPCode cache
eAccellerator, APC, Xcache, ionCube, Turck MMCache, Zend, etc..
There are MANY different OPCode cache that can
be installed for PHP, some are new, and some
are well seasoned.
My favorite are the ones that use shared memory to
reduce slow disk accesses.
I have tested different ones, my current favorite is
APC with PHP 5.3

15. BEST OPTIMIZATION?
Done all of this but PHP is still slow ?
You can optimize your PHP code and install
OPCode cache but if you still have issues you can
check the followings:
●
Database Queries
●
Disk accesses (fopen, dir, etc.)
●
Network (DNS, open on URLs, etc.)
●
Memory usage (memory_get_usage, memory_get_peak_usage)
●
Modules Installed
●
Endless Loops, Bugs