Php code optimization suggestions

Php code optimization recommendations from: http://blog.csdn.net//wgw335363240/article/details/41844879

Use single quotes instead of double quotes to include strings, which is faster. Because PHP will search for variables in strings enclosed by double quotes, but not in single quotes. Note: Only echo can do this, it is a "function" that can treat multiple strings as parameters (echo is a language structure, not a real function, so double quotation marks are added to the function ).

1. if the class method can be defined as static, it should be defined as static as much as possible, and its speed will be increased by nearly four times.

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

3. echo is faster than print, and multiple echo parameters are used to replace string connections, such as echo $ str1, $ str2.

4. determine the maximum number of cycles before executing the for loop. do not calculate the maximum value for each loop. use foreach instead.

5. cancel unnecessary variables, especially large arrays, to release the memory.

6. avoid using _ get ,__ set ,__ autoload whenever possible.

7. require_once () is expensive.

8. try to use the absolute path when you include the file, because it avoids PHP's speed of searching for the file in include_path, and it takes less time to parse the operating system path.

9. if you want to know the TIME when the script starts to be executed (I .e. when the SERVER receives a client REQUEST), use $ _ SERVER ['request _ time'] instead of time ().

10. functions use the same functions instead of regular expressions.

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 exchange function can take an array or character as a parameter and the length of the parameter is not too long, you can consider writing an additional segment of exchange code so that each input parameter is a character, instead of writing only one line of code to accept arrays as query and exchange parameters.

13. Using the select branch statement is better than using multiple if and else if statements.

14. blocking error messages with @ is very inefficient and extremely inefficient.

15. open the mod_deflate module of apache to speed up web page browsing.

16. when the database connection is used up, it should be switched off. do not use persistent connections.

17. the error message is expensive.

18. increment local variables in the method at the fastest speed. It is almost the same as calling a local variable in a function.

19. increasing a global variable is twice slower than increasing a local variable.

20. incrementing an object property (for example, $ this-> prop ++) is three times slower than incrementing a local variable.

21. increasing an unspecified local variable is 9 to 10 times slower than increasing a predefined local variable.

22. defining only one local variable without calling it in the function also slows down (to the extent that it is equivalent to increasing a local variable ). PHP will probably check whether global variables exist.

23. method calls seem to have nothing to do with the number of methods defined in the class, because I have added 10 methods before and after the test method, but the performance has not changed.

24. the method in the derived class runs faster than the same method defined in the base class.

25. calling an empty function with a parameter takes seven to eight times to increment local variables. Similar methods call local variable increment operations that take nearly 15 times.

26. Apache parses a PHP script two to ten times slower than parsing a static HTML page. Use static HTML pages and less scripts as much as possible.

27. unless the script can be cached, it will be re-compiled every time it is called. The introduction of a PHP Cache mechanism can generally improve the performance by 25% to 100%, so as to avoid compilation overhead.

28. use memcached as much as possible. Memcached is a high-performance memory object cache system that can accelerate dynamic Web applications and reduce database load. It is useful for the cache of OP code, so that the script does not have to re-compile each request.

29. when operating a string and checking whether its length meets certain requirements, you will use the strlen () function. This function is executed quite quickly because it does not perform any calculations and only returns the known string length stored in the zval structure (C's built-in data structure, used to store PHP variables. However, because strlen () is a function, it is more or less slow, because function calls take many steps, such as lowercase letters, PHP does not distinguish between case-insensitive function names.) and hash searches are executed along with the called function. In some cases, you can use isset () technology to accelerate your code execution.

(For example)

If (strlen ($ foo) <5) {echo "Foo is too short" $}

(Compare with the following technologies)

If (! Isset ($ foo {5}) {echo "Foo is too short" $}

Calling isset () happens to be faster than strlen (), because unlike the latter, isset () is used as a language structure, this means that function search and lowercase letters are not required for execution. That is to say, in fact, you do not spend too much money in the top-level code that checks the string length.

34. when the execution variable $ I increments or decreases, $ I ++ is slower than ++ $ I. This difference is exclusive to PHP and does not apply to other languages. therefore, do not modify your C or Java code and expect them to become faster and useless immediately. ++ $ I is faster because it only requires three commands (opcodes), and $ I ++ requires four commands. In fact, a temporary variable is generated in post-increment mode, which is then incremented. The pre-increment directly increases on the original value. This is a kind of optimization, as the Zend PHP optimizer does. Keeping this optimization processing in mind is a good idea, because not all command optimizers perform the same optimization, and there are a large number of Internet service providers (ISPs) without command optimizers) and server.

35. it is not object-oriented (OOP). object-oriented usually has a high overhead, and each method and object call will consume a lot of memory.

36. arrays are also useful instead of using classes to implement all data structures.

37. do not subdivide the method too much. think carefully about the code you actually intend to reuse?

38. when you need it, you can always break down the code into methods.

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 using C extension to implement them.

41. profile your code. The validator will tell you how much time the code consumes. The Xdebug debugger contains an inspection program, which can display the code bottleneck in general.

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

43. when file_get_contents can be used to replace file, fopen, feof, fgets, and other methods, try to use file_get_contents, because its efficiency is much higher! Note the PHP version of file_get_contents when opening a URL file;

44. perform as few file operations as possible, although PHP file operations are not efficient;

45. optimize Select SQL statements and perform Insert and Update operations as little as possible (I have been maliciously approved in update );

46. try to use PHP internal functions as much as possible (however, in order to find a function that does not exist in PHP, it is a waste of time to write a user-defined function. this is an empirical problem !);

47. do not declare variables inside the loop, especially big variables: objects (doesn't this seem to be a concern in PHP ?);

48. do not use nested values for multi-dimensional arrays;

49. do not use regular expressions when using internal PHP strings to operate functions;

50. foreach is more efficient. use foreach instead of the while and for loops;

51. use single quotes instead of double quotes to reference strings;

52. replace I = I + 1 with I + = 1. In line with the c/c ++ habits, high efficiency ";

53. for global variables, unset () should be used up;

Finally, summarize the common and important php optimization strategies:

1. use absolute paths in pair Des and requires, so that the analysis path takes less time;

2. do not use functions in the loop, For example, For ($ x = 0; $ x <count ($ array); $ x), and count () functions are calculated first;

3. use the error_reporting (0) function to prevent potential sensitive information from being displayed to users. Ideal error reports should be completely disabled in the php. ini file. However, if you are using a shared virtual host. ini you cannot modify, so you 'd better add the error_reporting (0) function and put it in the first line of each script file (or load it using require_once) this effectively protects sensitive SQL queries and paths from being displayed when an error occurs;

4. too many loop sets are prohibited, and too many nested loops will reduce execution efficiency.

5. it is prohibited to execute related query statements within the loop. Unless ten thousand cannot, ten thousand cannot do so.

6. try to use single quotes to join strings

7. minimize the number of variable copy operations. Example: $ description = $ _ POST ['description'];

8. when there are too many if/else, try to use switch/case instead of if/else. Make the code more concise

9. enabling the cache mechanism helps improve performance and reduce MySQL load

10. enable gzip compression