Analyze 50 tips to improve PHP execution efficiency, _PHP tutorial

Analysis of 50 tips to improve PHP execution efficiency,

1. Use single quotes instead of double quotes to include strings, which will be faster. Because PHP will search for variables in strings surrounded by double quotes, single quotes will not. Note: only echo can do this, it is a "function" that can take multiple strings as parameters (Annotation: PHP Manual It is said that echo is a language structure, not a real function, so the function is enclosed in double quotes).

2. If you can define a class method as static, try to define it as static, and its speed will be increased by nearly 4 times.

3. The speed of $row[‘id’] is 7 times that of $row[id].

4. 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.

5. 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.

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

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

8. require_once() is expensive.

9. 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.

10. If you want to know the moment when the script starts executing (annotation: the server receives the client request), use

$_SERVER[‘REQUEST_TIME’] is better than time()

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

12. 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.

13. If a string replacement function can accept arrays or characters as parameters, and the parameter length is not too long, then 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.

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

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

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

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

18. Error messages are expensive.

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

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

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

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

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

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

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

26. 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 increments.

27. 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.

28. 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.

29. 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.

30. 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 lookup and letter lowercase. That is, you actually don't spend much overhead in the top-level code checking the string length.

31. 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 perform the same optimizations, and there are a large number of Internet Service Providers (ISPs) and servers that do not have command optimizers installed.

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

33. It is not necessary to use classes to implement all data structures, arrays are also very useful.

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

35. You can always break the code into methods when you need it.

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

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

38. 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.

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

40. 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 pay attention to the PHP version problem of file_get_contents when opening a URL file. ;

41. Conduct file operations as little as possible, although PHP’s file operations are not inefficient;

42. Optimize the Select SQL statement and perform as few Insert and Update operations as possible (I was criticized for updating);

43. 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 by writing a custom function. It is a matter of experience!);

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

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

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

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

48. Use single quotes instead of double quotes to quote strings;

49. "Replace i=i 1 with i =1. It conforms to the c/c habit and is more efficient";

50. Global variables should be unset()ed when used.
51. Use checkdnsrr() to confirm the validity of some email addresses through the existence of domain names. This built-in function can ensure that each domain name corresponds to an IP address;
52. If you are using php5 and mysql4.1 or above, consider using the improved function mysqli_; of mysql_
53. Use highlight_file() to automatically print a well-formatted copy of the page source code;
54. Use the error_reporting(0) function to prevent potentially sensitive information from being displayed to the user. Ideally error reporting should be completely disabled in the php.ini file. But if you are using a For a shared virtual host, you cannot modify php.ini, so you'd better add the error_reporting(0) function and put it on the first line of each script file (or use require_once() to load) This can effectively protect sensitive SQL queries and paths from being displayed when errors occur;
55. Use the error_reporting(0) function to prevent potentially sensitive information from being displayed to the user. Ideally error reporting should be completely disabled in the php.ini file. But if you are using a For a shared virtual host, you cannot modify php.ini, so you'd better add the error_reporting(0) function and put it on the first line of each script file (or use require_once() to load) This can effectively protect sensitive SQL queries and paths from being displayed when errors occur;
56. A function can have multiple return values ​​by referencing parameter variable addresses. You can add an "&" before the variable to indicate passing it by address rather than by value;
57. Turn off the PHP Magic Quote function. Not every piece of escaped data must be inserted into the database. If all the data entered into PHP If all the data is escaped, it will have a certain impact on the execution efficiency of the program. It is more efficient to call escape functions (such as addslashes()) at runtime

58. Use the ip2long() and long2ip() functions to convert the IP address into an integer and store it in the database instead of a character. This reduces storage space by almost 1/4. At the same time, addresses can be easily sorted and quickly searched;

59. Use gzcompress() and gzuncompress() to compress (decompress) large-capacity strings when storing (retrieving) the database. This built-in function can compress up to 90% using the gzip algorithm;

60. Use checkdnsrr() to confirm the validity of some email addresses through domain name existence. This built-in function ensures that each domain name corresponds to an IP address.

61, isset is used instead of strlen in some places

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”$$ }
(Compare with the following technique)
if (!isset($foo{5})) { echo “Foo is too short”$$ }
Calling isset() happens to be faster than strlen(), because unlike the latter, isset() Being a language construct means that its execution does not require function lookups and letter lowercasing. That is, you actually don't spend much overhead in the top-level code checking the string length.