PHP Optimization Tips

Kamalakannan · #41 (**permalink**) 11-07-2007, 02:07 AM

Hi,

Set the maxvalue for your for-loops before and not in the loop.

Code:

$maxvalue = 100/10;
for($i=0; $i<$maxvalue; $i++){
   // Some code
}

is faster than:

Code:

for($i=0; $i<100/10; $i++){
   // Some code
}

because the value is calculated once instead of ten times.

Regards,
R.Kamalakannan.

Kamalakannan · #42 (**permalink**) 11-07-2007, 02:26 AM

Hi,

Many code blocks might slow down the interpretation a little bit.

Code:

<?
   ...
   ...
   ...
?>

is faster than

Code:

<? ... ?>
<? ... ?>
<? ... ?>

Regards,
R.Kamalakannan.

Jeyaseelansarc · #43 (**permalink**) 11-07-2007, 04:47 AM

if you want to assign variable to one of the array indexes, don’t do $var=$arr[‘foo’], better choice would be use references. $var=&$arr[‘foo’], now you just creating a reference to $arr[‘foo’] instead of duplicating it’s value.

use $_SERVER[’REQUEST_TIME’] instead of every time calling time() function. For example declare constant at the config file: define(“TIME”, $_SERVER[’REQUEST_TIME’]) and use TIME when you want to know timestamp.

Jeyaseelansarc · #44 (**permalink**) 11-07-2007, 04:48 AM

ctype functions are faster than regular expressions. More info at PHP: Character Type Functions - Manual

Jeyaseelansarc · #45 (**permalink**) 11-07-2007, 05:24 AM

- $arr[‘id’] works much more faster than $arr[id]
- if you need to print a bigger piece of text without PHP variables just exit PHP (?>) and enter it when you need it again (<?php).

Gopisoft · #46 (**permalink**) 11-08-2007, 03:54 AM

Hi,

Compiler/Opcode Caches

This cycle happens for every include file, not just for the "main" script.
Compilation can easily consume more time than execution.
Each PHP script is compiled only once for each revision.
Reduced File IO, opcodes are being read from memory instead of being parsed from disk.
Opcodes can optimised for faster execution.

Thanks,
R.Gopi.

Gopisoft · #47 (**permalink**) 11-08-2007, 04:13 AM

Hi,

Optimize the Web Server File I/O Operations

Keep DirectoryIndex file list as short as possible.
Whenever possible disable .htaccess via AllowOverride none.
Use Options FollowSymLinks to simplify file access process in Apache.
If logs are unnecessary disable them.
If logging is a must, log everything to 1 file and break it up during the analysis stage.

Thanks,
R.Gopi.

Gopisoft · #48 (**permalink**) 11-08-2007, 04:17 AM

Hi,

Tuning PHP Configuration

register_globals = Off **
magic_quotes_gpc = Off
expose_php = Off
register_argc_argv = Off
always_populate_raw_post_data = Off **
session.use_trans_sid = Off **
session.auto_start = Off **
session.gc_divisor = 1000 or 10000
output_buffering = 4096

Thanks,
R.Gopi

Gopisoft · #49 (**permalink**) 11-08-2007, 04:27 AM

Hi,

Tips of Tuning PHP Including / File Accessing

Whenever opening files or including scripts into the main script try to specify a full path or at least an easily resolvable partial path.

Inefficient Approach:

PHP Code:

<?php include "file.php"; ?>

Performance Friendly Approach:

PHP Code:

  <?php

include "/path/to/file.php";

// or

include "./file.php";

?>

Thanks,
R.Gopi.

Gopisoft · #50 (**permalink**) 11-08-2007, 04:47 AM

Hi,
Optimizing the str_replace()
The str_replace() function in PHP can be slow, due it’s duplication of data even if no replacement is being performed.

PHP Code:

  $src_str = file_get_contents("CONTENT_FILE_PATH");

$src = array('abc', 123, 'text');

$dst = array('cba', 321, 'txet');

// eliminate unnecessary replacement attempts

foreach ($src as $k => $v)

if (strpos($src_str, $src) === FALSE)

unset($src[$k], $dst[$k]);

if ($src) $new_str = str_replace($src, $dst, $src_str);

Click to view the difference of strtr() and str_replace()

Thanks,
R.Gopi

Gopisoft · #51 (**permalink**) 11-08-2007, 09:35 PM

HI,

Web Server: Syscalls

Syscall is function executed by the Kernel. The goal is to minimise the number of these calls needed to perform a request.

Do not enable ExtendedStatus.
For Deny/Allow rules use IPs rather then domains.
Do not enable HostnameLookups.
Keep ServerSignature off

Thanks,
R.Gopi.

Jeyaseelansarc · #52 (**permalink**) 11-09-2007, 10:40 PM

Some more useful tips
* printf is much more slower than echo or print, it must handle additional parameters. But echo is faster than print, despite of that both are constructors, print is returning boolean result, echo returns nothing.
* when searching string in another string strstr() is faster than preg functions, however if you want to know if that string exists use strpos().

Sabari · #53 (**permalink**) 11-12-2007, 04:09 AM

How many ways your web server can utilize PHP to generate web pages?

Mainly there are three ways
***************************

The first method is to use PHP as a CGI "wrapper". When run this way, an instance of the PHP interpreter is created and destroyed for every page request (for a PHP page) to your web server. Because it is destroyed after every request, any resources that it acquires (such as a link to an SQL database server) are closed when it is destroyed. In this case, you do not gain anything from trying to use persistent connections -- they simply don't persist.

The second, and most popular, method is to run PHP as a module in a multiprocess web server, which currently only includes Apache. A multiprocess server typically has one process (the parent) which coordinates a set of processes (its children) who actually do the work of serving up web pages. When a request comes in from a client, it is handed off to one of the children that is not already serving another client. This means that when the same client makes a second request to the server, it may be served by a different child process than the first time. When opening a persistent connection, every following page requesting SQL services can reuse the same established connection to the SQL server.

The last method is to use PHP as a plug-in for a multithreaded web server. Currently PHP 4 has support for ISAPI, WSAPI, and NSAPI (on Windows), which all allow PHP to be used as a plug-in on multithreaded servers like Netscape FastTrack (iPlanet), Microsoft's Internet Information Server (IIS), and O'Reilly's WebSite Pro. The behavior is essentially the same as for the multiprocess model described before. Note that SAPI support is not available in PHP 3.

Sabari · #54 (**permalink**) 11-14-2007, 10:26 PM

Hi Gopi,

your posts are very very useful for us, so please keep on postions these kind of valuable posts.

Sabari · #55 (**permalink**) 11-14-2007, 10:50 PM

PHP is a very fast programming language, but there is more to optimizing PHP than just speed of code execution.

here, we explain why optimizing PHP involves many factors which are not code related, and why tuning PHP requires an understanding of how PHP performs in relation to all the other subsystems on your server, and then identifying bottlenecks caused by these subsystems and fixing them. We also cover how to tune and optimize your PHP scripts so they run even faster.

Sabari · #56 (**permalink**) 11-14-2007, 10:52 PM

Achieving High Performance

When we talk about good performance, we are not talking about how fast your PHP scripts will run. Performance is a set of tradeoffs between scalability and speed. Scripts tuned to use fewer resources might be slower than scripts that perform caching, but more copies of the same script can be run at one time on a web server.

In the example below, A.php is a sprinter that can run fast, and B.php is a marathon runner than can jog forever at the nearly the same speed. For light loads, A.php is substantially faster, but as the web traffic increases, the performance of B.php only drops a little bit while A.php just runs out of steam.

Let us take a more realistic example to clarify matters further. Suppose we need to write a PHP script that reads a 250K file and generates a HTML summary of the file. We write 2 scripts that do the same thing: hare.php that reads the whole file into memory at once and processes it in one pass, and tortoise.php that reads the file, one line at time, never keeping more than the longest line in memory. Tortoise.php will be slower as multiple reads are issued, requiring more system calls.

Hare.php requires 0.04 seconds of CPU and 10 Mb RAM and tortoise.php requires 0.06 seconds of CPU and 5 Mb RAM. The server has 100 Mb free actual RAM and its CPU is 99% idle. Assume no memory fragmentation occurs to simplify things.

At 10 concurrent scripts running, hare.php will run out of memory (10 x 10 = 100). At that point, tortoise.php will still have 50 Mb of free memory. The 11th concurrent script to run will bring hare.php to its knees as it starts using virtual memory, slowing it down to maybe half its original speed; each invocation of hare.php now takes 0.08 seconds of CPU time. Meanwhile, tortoise.php will be still be running at its normal 0.06 seconds CPU time.

Sabari · #57 (**permalink**) 11-14-2007, 10:57 PM

In the table below, the faster php script for different loads is in bold:

----------------------------------------------------------------------------------------------
Connections | CPU seconds required to satisfy 1 HTTP request | CPU seconds required to satisfy 10 HTTP requests | CPU seconds required to satisfy 11 HTTP requests |
----------------------------------------------------------------------------------------
hare.php | 0.04 | 0.40 | 0.88 (runs out of RAM)
----------------------------------------------------------------------------------------
tortoise.php | 0.06 | 0.60 | 0.66
----------------------------------------------------------------------------------------

As the above example shows, obtaining good performance is not merely writing fast PHP scripts. High performance PHP requires a good understanding of the underlying hardware, the operating system and supporting software such as the web server and database.

Sabari · #58 (**permalink**) 11-14-2007, 11:02 PM

Bottlenecks
The hare and tortoise example has shown us that bottlenecks cause slowdowns. With infinite RAM, hare.php will always be faster than tortoise.php. Unfortunately, the above model is a bit simplistic and there are many other bottlenecks to performance apart from RAM:

Sabari · #59 (**permalink**) 11-14-2007, 11:02 PM

(a) Networking
Your network is probably the biggest bottleneck. Let us say you have a 10 Mbit link to the Internet, over which you can pump 1 megabyte of data per second. If each web page is 30k, a mere 33 web pages per second will saturate the line.

More subtle networking bottlenecks include frequent access to slow network services such as DNS, or allocating insufficient memory for networking software.

Sabari · #60 (**permalink**) 11-14-2007, 11:03 PM

(b) CPU
If you monitor your CPU load, sending plain HTML pages over a network will not tax your CPU at all because as we mentioned earlier, the bottleneck will be the network. However for the complex dynamic web pages that PHP generates, your CPU speed will normally become the limiting factor. Having a server with multiple processors or having a server farm can alleviate this.

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