HOBALL 筆記簿

April 1, 2010

PHP: Run two foreach loops at the same time

Filed under: PHP — Tags: , , , — hoball @ 11:25 am

@reference: http://stackoverflow.com/questions/2556998/how-do-you-combine-two-foreach-loops-into-one

SPL MultipleIterator
@reference: http://docs.php.net/class.multipleiterator

// ArrayIterator is just an example, could be any Iterator.
$a1 = new ArrayIterator(array(1, 2, 3, 4, 5, 6));
$a2 = new ArrayIterator(array(11, 12, 13, 14, 15, 16));

$it = new MultipleIterator;
$it->attachIterator($a1);
$it->attachIterator($a2);

foreach($it as $e) {
  echo $e[0], ' | ', $e[1], "\n";
}

Prints

1 | 11
2 | 12
3 | 13
4 | 14
5 | 15
6 | 16

March 12, 2010

ip2long vs INET_ATON

Filed under: PHP, SQL — Tags: , , , — hoball @ 9:15 pm

Source: http://mwillis.co.uk/mysql/ip2long-vs-inet_aton/

PHP ip2long() sometimes return negative integers,
while MySQL INET_ATON() function returns only positive numbers.

Ensure PHP ip2long() returns only positive intergers:

sprintf("%u", ip2long("254.254.254.254"));
$ip = ip2long($ip_address);
if ($ip < 0){ $ip += 4294967296; }

September 29, 2009

HTML Tidy on linux under XAMPP

Filed under: PHP — Tags: , , , — hoball @ 11:53 pm

Installing tidy on PHP5 under linux is pain. The manual says  “compile with –with-tidy”, but it is not really happening.

Finally I made it work on my fedora (using XAMPP) by this method:

# Install libtidy
yum -y install tidy

# Download PHP 5 source
http://www.php.net/downloads.php

# Unpack the source
tar xvzf php-5.3.0.tar.gz

# Configure tidy for installed php5 API
cd php-5.3.0/ext/tidy
/opt/lampp/bin/phpize

# Stay at the same folder, Configure & Compile the source
./configure --with-php-config=/opt/lampp/bin/php-config --with-tidy
make clean    <-- Without this the compile builds a bad module for some reason
make
make install

# Install module into php.ini - Add:: extension="tidy.so"
vi /opt/lampp/etc/php.ini

References:

ubuntuforums.org: LAMP: php5-tidy doesn’t exist!

newsn.net 给AndLinux下面的xampp装tidy模块的经验 (Chinese)

/opt/lampp/etc/php.i

December 31, 2008

PHP Multi-Threads / Multi-Processes

Filed under: PHP — Tags: , , , , , — hoball @ 4:51 pm

By the use of curl_multi_init() (PHP5) or stream_select() (PHP5) or  pcntl_fork (PHP4+), we can stimulate multi-thread/multi-process environment on PHP

External Links:

using stream_select: Develop multitasking applications with PHP V5

using curl_multi_init: PHP curl_multi example of parallel GET requests

using pcntl_fork (chinese): 多采多姿的程式筆記#1, #2

forum quote(chinese): EcStart PHP 技術討論論壇

PHP是與host環境相關的腳本語言,通常狀況下不會使用thread的,有的話也是host的問題,與php沒有關係。(你用的話,會有同步等等問題,甚至會有可能造成host運作不穩定)

但是如果把php當作shell script等等獨立的語言工具來用的話,是可以模擬的。

php本身應該沒有提供thread的函數,但是有multi-process的吧。

請用google找找。

我在酷學園有看過一些討論:
http://phorum.study-area.org/index.php/topic,44942.0.html
http://phorum.study-area.org/index.php/topic,47238.0.html(這篇有提到一點同步機制)

另外,參考一下這一篇:
http://www.ibm.com/developerworks/web/library/os-php-multitask/?ca=dgr-lnxw06PHP5multitasking
(用php5模擬多工)

December 7, 2008

PHP Exceptions

Filed under: PHP — Tags: , , , — hoball @ 10:02 pm

Part 1: http://i-novice.com/php-exceptions-part-1/

Part 2: http://i-novice.com/php-exceptions-part-2/

PHP variables, Memory Handling

Filed under: PHP — Tags: , , , , , — hoball @ 9:51 pm

Adam Charnock: The Truth About PHP Variables

Sara Golemon: How to Manage Memory in PHP

October 31, 2008

PHP *_once vs require/include

Filed under: PHP — Tags: , , , , — hoball @ 4:08 pm

There are criticisms that require_once/include_once are slow. To speed up them, I find this solution from http://www.php.net/require_once

antoine dot pouch at mcgill dot ca
10-Mar-2006 11:13

require_once (and include_once for that matters) is slow.
Furthermore, if you plan on using unit tests and mock objects (i.e. including mock classes before the real ones are included in the class you want to test), it will not work as require() loads a file and not a class.

To bypass that, and gain speed, I use :

<?php
class_exists(‘myClass’) || require(‘path/to/myClass.class.php’);
?>

I tried to time 100 require_once on the same file and it took the script 0.0026 seconds to run, whereas with my method it took only 0.00054 seconds. 4 times faster ! OK, my method of testing is quite empirical and YMMV but the bonus is the ability to use mock objects in your unit tests.

Reference: http://www.php.net/manual/en/language.operators.logical.php

40 Tips for optimizing your php code

Filed under: PHP — Tags: , , — hoball @ 3:19 pm

Quoted from here

  1. If a method can be static, declare it static. Speed improvement is by a factor of 4.
  2. echo is faster than print.
  3. Use echo’s multiple parameters instead of string concatenation.
  4. Set the maxvalue for your for-loops before and not in the loop.
  5. Unset your variables to free memory, especially large arrays.
  6. Avoid magic like __get, __set, __autoload
  7. require_once() is expensive
  8. Use full paths in includes and requires, less time spent on resolving the OS paths.
  9. If you need to find out the time when the script started executing, $_SERVER[’REQUEST_TIME’] is preferred to time()
  10. See if you can use strncasecmp, strpbrk and stripos instead of regex
  11. str_replace is faster than preg_replace, but strtr is faster than str_replace by a factor of 4
  12. If the function, such as string replacement function, accepts both arrays and single characters as arguments, and if your argument list is not too long, consider writing a few redundant replacement statements, passing one character at a time, instead of one line of code that accepts arrays as search and replace arguments.
  13. It’s better to use switch statements than multi if, else if, statements.
  14. Error suppression with @ is very slow.
  15. Turn on apache’s mod_deflate
  16. Close your database connections when you’re done with them
  17. $row[’id’] is 7 times faster than $row[id]
  18. Error messages are expensive
  19. Do not use functions inside of for loop, such as for ($x=0; $x < count($array); $x) The count() function gets called each time.
  20. Incrementing a local variable in a method is the fastest. Nearly the same as calling a local variable in a function.
  21. Incrementing a global variable is 2 times slow than a local var.
  22. Incrementing an object property (eg. $this->prop++) is 3 times slower than a local variable.
  23. Incrementing an undefined local variable is 9-10 times slower than a pre-initialized one.
  24. Just declaring a global variable without using it in a function also slows things down (by about the same amount as incrementing a local var). PHP probably does a check to see if the global exists.
  25. Method invocation appears to be independent of the number of methods defined in the class because I added 10 more methods to the test class (before and after the test method) with no change in performance.
  26. Methods in derived classes run faster than ones defined in the base class.
  27. A function call with one parameter and an empty function body takes about the same time as doing 7-8 $localvar++ operations. A similar method call is of course about 15 $localvar++ operations.
  28. Surrounding your string by ‘ instead of ” will make things interpret a little faster since php looks for variables inside “…” but not inside ‘…’. Of course you can only do this when you don’t need to have variables in the string.
  29. When echoing strings it’s faster to separate them by comma instead of dot. Note: This only works with echo, which is a function that can take several strings as arguments.
  30. A PHP script will be served at least 2-10 times slower than a static HTML page by Apache. Try to use more static HTML pages and fewer scripts.
  31. Your PHP scripts are recompiled every time unless the scripts are cached. Install a PHP caching product to typically increase performance by 25-100% by removing compile times.
  32. Cache as much as possible. Use memcached – memcached is a high-performance memory object caching system intended to speed up dynamic web applications by alleviating database load. OP code caches are useful so that your script does not have to be compiled on every request
  33. When working with strings and you need to check that the string is either of a certain length you’d understandably would want to use the strlen() function. This function is pretty quick since it’s operation does not perform any calculation but merely return the already known length of a string available in the zval structure (internal C struct used to store variables in PHP). However because strlen() is a function it is still somewhat slow because the function call requires several operations such as lowercase & hashtable lookup followed by the execution of said function. In some instance you can improve the speed of your code by using an isset() trick.Ex.if (strlen($foo) < 5) { echo “Foo is too short”; }

    vs.

    if (!isset($foo{5})) { echo “Foo is too short”; }

    Calling isset() happens to be faster then strlen() because unlike strlen(), isset() is a language construct and not a function meaning that it’s execution does not require function lookups and lowercase. This means you have virtually no overhead on top of the actual code that determines the string’s length.

  34. When incrementing or decrementing the value of the variable $i++ happens to be a tad slower then ++$i. This is something PHP specific and does not apply to other languages, so don’t go modifying your C or Java code thinking it’ll suddenly become faster, it won’t. ++$i happens to be faster in PHP because instead of 4 opcodes used for $i++ you only need 3. Post incrementation actually causes in the creation of a temporary var that is then incremented. While pre-incrementation increases the original value directly. This is one of the optimization that opcode optimized like Zend’s PHP optimizer. It is a still a good idea to keep in mind since not all opcode optimizers perform this optimization and there are plenty of ISPs and servers running without an opcode optimizer.
  35. Not everything has to be OOP, often it is too much overhead, each method and object call consumes a lot of memory.
  36. Do not implement every data structure as a class, arrays are useful, too
  37. Don’t split methods too much, think, which code you will really re-use
  38. You can always split the code of a method later, when needed
  39. Make use of the countless predefined functions
  40. If you have very time consuming functions in your code, consider writing them as C extensions
  41. Profile your code. A profiler shows you, which parts of your code consumes how many time. The Xdebug debugger already contains a profiler. Profiling shows you the bottlenecks in overview
  42. mod_gzip which is available as an Apache module compresses your data on the fly and can reduce the data to transfer up to 80%
  43. Excellent Article about optimizing php by John Lim

October 21, 2008

代碼小技巧:一鍵註釋

Filed under: Coding/Programming — Tags: , , , — hoball @ 12:55 pm

轉載自 http://www.cnblogs.com/biggates/archive/2008/02/28/1085216.html

書寫(和調試)大段大段的代碼的過程中,經常遇到頻繁的註釋和取消註釋的麻煩吧。今天在Ajaxian上學到一招,可以非常方便地對代碼進行註釋和取消註釋:

foo();
/**//*
bar();
baz.foo = 200;
return{
dolly:clone()
}
//
*/

簡單地說,就是把表示區塊註釋的 /* 和 */  改成  /* 和 //*/ ,代碼的修改量只有一個 // 而已。

之後,只要在 /* 的前面加上或刪除一個 / ,就能切換整塊註釋的狀態了。

foo();
//*
bar();
baz.foo
= 200;
return{
dolly:clone()
}

// */


October 18, 2008

PHP Performance Best Practice

Filed under: PHP — Tags: , — hoball @ 9:06 pm

http://atomized.org/2005/04/php-performance-best-practices/

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