Optimization definition and code optimization in php

The article summarizes the optimization suggestions and code optimization in PHP, and has good suggestions for PHP programmers

1. If you can define the class method as static, try to define it as static, its speed It will increase nearly 4 times.

2. $row[’id’] is 7 times faster than $row[id].

3. Echo is faster than print, and uses multiple parameters of echo (annotation: refers to using commas instead of periods) instead of string concatenation, such as echo $str1, $str2.

4. Determine the maximum number of loops before executing the for loop. Do not calculate the maximum value every loop. It is best to use foreach instead.

5. Unregister unused variables, especially large arrays, to free up memory.

6. Try to avoid using __get, __set, __autoload.

7. require_once() is expensive.

8. Try to use absolute paths when including files, because it avoids the speed of PHP searching for files in include_path, and the time required to parse the operating system path will be less.

9. If you want to know the time when the script starts executing (annotation: that is, the server receives the client request), it is better to use $_SERVER[‘REQUEST_TIME’] than time().

10. Functions replace regular expressions to complete the same function.

11. The str_replace function is faster than the preg_replace function, but the strtr function is four times more efficient than the str_replace function.

12. If a string replacement function accepts arrays or characters as parameters, and the parameter length is not too long, you can consider writing an additional replacement code so that each parameter passed is one character instead of just one line. The code accepts arrays as parameters for query and replace.

13. It is better to use a selective branch statement (translation annotation: switch case) than to use multiple if, else if statements.

14. Using @ to block error messages is very inefficient, extremely inefficient.

15. Opening the mod_deflate module of apache can improve the browsing speed of web pages.

16. The database connection should be closed when finished using it, and do not use long connections.

17. Error messages are expensive.

18. Increasing local variables in methods is the fastest. Almost as fast as calling local variables in a function.

19. Incrementing a global variable is 2 times slower than incrementing a local variable.

20. Incrementing an object property (such as: $this->prop++) is 3 times slower than incrementing a local variable.

21. Incrementing an undefined local variable is 9 to 10 times slower than incrementing a predefined local variable.

22. Just defining a local variable without calling it in a function will also slow down (to the same extent as incrementing a local variable). PHP will probably check to see if a global variable exists.

23. Method calls appear to be independent of the number of methods defined in the class, as I added 10 methods (both before and after testing the method), but there was no change in performance.

24. Methods in derived classes run faster than the same methods defined in base classes.

25. Calling an empty function with one parameter takes the same time as performing 7 to 8 local variable increment operations. A similar method call takes close to 15 local variable increment operations.

26. The time it takes for Apache to parse a PHP script is 2 to 10 times slower than parsing a static HTML page. Try to use more static HTML pages and less scripts.

27. Unless the script can be cached, it will be recompiled every time it is called. Introducing a PHP caching mechanism can usually improve performance by 25% to 100% to eliminate compilation overhead.

28. Try to cache as much as possible, you can use memcached. Memcached is a high-performance memory object caching system that can be used to accelerate dynamic web applications and reduce database load. Caching of OP codes is useful so that scripts do not have to be recompiled for each request.

29. When operating a string and need to check whether its length meets certain requirements, you will naturally use the strlen() function. This function executes quite quickly because it does not do any calculations and just returns the known string length stored in the zval structure (C's built-in data structure used to store PHP variables). However, since strlen() is a function, it will be somewhat slow, because the function call will go through many steps, such as lowercase letters (Annotation: refers to the lowercase function name, PHP does not distinguish between uppercase and lowercase function names), hash search, Will be executed together with the called function. In some cases, you can use the isset() trick to speed up the execution of your code.
(Example below)
if (strlen($foo) < 5) { echo “Foo is too short”$$ }
(Compare with the tips below)
if (!isset($foo{5})) { echo “Foo is too short”$$ }
Calling isset() happens to be faster than strlen() because, unlike the latter, isset(), as a language construct, means that its execution does not require function lookups and lowercase letters. That is, you actually don't spend much overhead in the top-level code checking the string length.

34. When executing the increment or decrement of variable $i, $i++ will be slower than ++$i. This difference is specific to PHP and does not apply to other languages, so please don't modify your C or Java code and expect it to be instantly faster, it won't work. ++$i is faster because it only requires 3 instructions (opcodes), while $i++ requires 4 instructions. Post-increment actually creates a temporary variable that is subsequently incremented. Prefix increment increases directly on the original value. This is a form of optimization, as done by Zend's PHP optimizer. It's a good idea to keep this optimization in mind because not all command optimizers do the same optimizations, and there are a large number of Internet Service Providers (ISPs) and servers that don't have command optimizers installed.

35. Not everything must be object-oriented (OOP), object-oriented is often very expensive, and each method and object call consumes a lot of memory.

36. It is not necessary to use classes to implement all data structures. Arrays are also very useful.

37. Don’t subdivide the methods too much. Think carefully about which code you really intend to reuse?

38. You can always decompose code into methods when you need to.

39. Try to use a large number of PHP built-in functions.

40. If there are a large number of time-consuming functions in the code, you can consider implementing them using C extensions.

41. Profile your code. The checker will tell you which parts of the code take how much time. The Xdebug debugger includes inspection routines that evaluate the overall integrity of your code and reveal bottlenecks in your code.

42. mod_zip can be used as an Apache module to instantly compress your data and reduce data transmission volume by 80%.

43. When file_get_contents can be used instead of file, fopen, feof, fgets and other series of methods, try to use file_get_contents because it is much more efficient! But please pay attention to the PHP version problem of file_get_contents when opening a URL file;

44. Conduct file operations as little as possible, although PHP’s file operation efficiency is not low;

45. Optimize the Select SQL statement and perform as few Insert and Update operations as possible (I was criticized on update);

46. Use PHP internal functions as much as possible (but in order to find a function that does not exist in PHP, I wasted time that could have been written a custom function, a matter of experience!);

47. Do not declare variables inside a loop, especially large variables: objects (this seems to be not just a problem in PHP, right?)

48. Try not to loop and nest assignments in multi-dimensional arrays

49. Do not use regular expressions when you can use PHP’s internal string manipulation functions

50. foreach is more efficient, try to use foreach instead of while and for loop

51. Use single quotes instead of double quotes to quote strings

52. Use i+=1 instead of i=i+1. It conforms to the habits of c/c++ and is highly efficient

53. For global variables, you should unset( ) them after use

Code optimization examples

In a function, when passing an array
Using return is more efficient than using global
For example

function userloginfo($usertemp){
$detail=explode("|",$usertemp);
return $detail;
}
$login=userloginfo($userdb);

than

function userloginfo($usertemp){
global $detail;
$detail=explode("|",$usertemp);
}
userloginfo($userdb);

Be efficient

2, (This code is used to get the URL corresponding to the program directory, recommended)

$urlarray=explode(@#/@#,$HTTP_SERVER_VARS[@#REQUEST_URI@#]);
$urlcount=count($urlarray);unset($urlarray[$urlcount-1]);
$ofstarurl=@#http://@#.$HTTP_SERVER_VARS[@#HTTP_HOST@#].implode(@#/@#,$urlarray);

This code is better than

$pre_urlarray=explode(@#/@#,$HTTP_SERVER_VARS[@#HTTP_REFERER@#]);
$pre_url=array_pop($pre_urlarray);

Be efficient

3. When judging in a loop, it is more efficient to use identity than equal to make numerical judgment
$a=2;$b=2;
For example
if($a==$b)$c=$a;
Than
if($a===$b)$c=$a;
Efficient

4. When querying mysql, try to use where in and use less limit
Limit searches the first few records of multiple records, which is very fast, but searches the top few records and it will be slower
Use in. When querying continuous records, it is very fast. The first run of non-continuous records will be a little slower, but it will be faster after that!

5, NT server data operation stability is not as stable as unix/linux

6. Try to use ob_start() before output; it can speed up the output. It is suitable for NT or nuli/linux. For unlix servers, if you use ob_start(@#ob_gzhandler@#); the output efficiency will be higher

7. Try to use if($a==his value) when judging and if(empty($a)) when negating, because this way the program runs faster

8, using unequal time != is as efficient as <>

9. From personal experience, the efficiency of using $a="11111111111111"; is equivalent to $a=@#11111111111111@#;. It is not very different as the book says

10. Using standardized SQL statements will help MySQL parsing

11, use

代码如下

复制代码

if($online){
$online1=$online;
setcookie(@#online1@#,$online,$cookietime,$ckpath,$ckdomain,$secure);
}

COOKIE将马上生效
使用

if($online)
setcookie(@#online1@#,$online,$cookietime,$ckpath,$ckdomain,$secure);

COOKIE needs to be refreshed again to take effect

12, use

The code is as follows

Copy code

代码如下

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$handle=fopen($filename,wb);
flock($handle,LOCK_SH);
$filedata=fread($handle,filesize($filename));
fclose($handle);

比

file($filename);

$handle=fopen($filename,wb);

flock($handle,LOCK_SH);

$filedata=fread($handle,filesize($filename));

fclose($handle);

代码如下

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比如$newarray[1]=substrs($newarray[1],25);

than

file($filename);

代码如下	复制代码
for ($asc=65;$asc<=90;$asc++) { //strtolower() 此函数在一些服务器会产生乱码! if (strrpos($regname,chr($asc))!==false) { $error="为了避免用户名混乱,用户名中禁止使用大写字母，请使用小写字母"; $reg_check=0; } }

Excellent in both speed and stability

代码如下	复制代码
function openfile($filename,$method="rb") { $handle=@fopen($filename,$method); @flock($handle,LOCK_SH); @$filedata=fread($handle,filesize($filename)); @fclose($handle); $filedata=str_replace(" "," ",$filedata); $filedb=explode("",$filedata); //array_pop($filedb); $count=count($filedb); if($filedb[$count-1]==@#){unset($filedb[$count-1]);} return $filedb; }

13, truncation string optimization function (can avoid the occurrence of ? characters)

The code is as follows	Copy code
function substrs($content,$length) { if(strlen($content)>$length){ $num=0; for($i=0;$i<$length-3;$i++) {<🎜> if(ord($content[$i])>127)$num++; } $num%2==1 ? $content=substr($content,0,$length-4):$content=substr($content,0,$length-3); $content.=@# ...@#; } return $content; } For example $newarray[1]=substrs($newarray[1],25);

14, case shielding in the program

The code is as follows	Copy code
for ($asc=65;$asc< =90;$asc++) { //strtolower() This function will produce garbled characters on some servers! if (strrpos($regname,chr($asc))!==false) { $error="In order to avoid confusion in usernames, uppercase letters are prohibited in usernames, please use lowercase letters"; $reg_check=0; } }

15, do not use file(); and do not use fget(); (unstable or slow) take an array function

The code is as follows	Copy code
function openfile($filename,$method=" rb") { $handle=@fopen($filename,$method); @flock($handle,LOCK_SH); @$filedata=fread($handle,filesize($filename)); @fclose($handle); $filedata=str_replace(" "," ",$filedata); $filedb=explode("",$filedata); //array_pop($filedb); $count=count($filedb); if($filedb[$count-1]==@#){unset($filedb[$count-1]);} return $filedb; }

//Although this function has a lot of code, it has great advantages in speed and stability!

Implement the above array separation code

After this, it is very convenient to access the block data of tempArray

array1[$row['ID']] = $row['Key'];

The code is as follows

代码如下

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foreach($tempArray as $row){

　　array1[$row['ID']] = $row['Key'];

　　array2[$row['Key']][] = $row;

}

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