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How to optimize php_PHP tutorial
- WBOYOriginal
- 2016-07-13 10:37:19653browse
PHP-Some performance optimization methods
0. 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).
PS: In single quotes, PHP will not automatically search for variables, escape characters, etc., so the efficiency is much faster. Generally speaking, strings do not have variables, so using double quotes will lead to poor performance.
1. 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.
PS: In fact, the speed of function, method, and static method will not be much different. For details, see the article "Implementation Principles and Performance Analysis of PHP Functions [Reprinted]".
2. $row[’id’] is 7 times faster than $row[id].
PS: I don’t quite understand. It seems that the only difference is that the latter will first determine whether the id macro exists, and if it does not exist, it will automatically be converted into a string.
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.
PS: If you use echo $str1.$str2, the PHP engine will first connect all the variables and then output them. When echo $str1, $str2, the PHP engine will output them in order
4. Determine the maximum number of loops before executing the for loop. Do not calculate the maximum value every loop. It is best to use foreach instead.
PS: Operations like count and strlen are actually O(1), so they will not cause too much consumption. Of course, it is a better strategy to avoid calculations every time it loops. It is best to use foreach instead of for, which is more efficient. If you consider the consumption of each copy of foreach($array as $var), you can use a reference like foreach($array as &$var).
5. Unregister unused variables, especially large arrays, to free up memory.
PS: If I remember correctly, unset($array) will not release the memory immediately, but it is a good habit to release it at any time.
6. Try to avoid using __get, __set, __autoload.
7. require_once() is expensive.
PS: require_once and include_once need to be heavily judged, so the efficiency is lower, but the efficiency problem has been basically solved after version 5.2.
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.
PS: Supported, use iniset() as little as possible to set include_path.
9. If you want to know the time when the script starts executing (annotation: the server receives the client request), it is better to use $_SERVER['REQUEST_TIME'] than time().
PS: $_SERVER['REQUEST_TIME'] saves the timestamp when the request is initiated, and time() returns the Unix timestamp of the current moment.
10. Functions replace regular expressions to complete the same function.
PS: This kind of function refers to strtok, strstr, strpos, str_replace, substr, explode, implode, etc.
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.
PS: String operation is faster than regular replacement.
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.
PS: You need to take into account the cost difference between built-in functions and user-defined functions. I’m afraid this approach outweighs the benefits.
13. It is better to use a selective branch statement (translation annotation: switch case) than to use multiple if, else if statements.
PS: switch in php supports numerical and string variables, which is easier to use than C's switch. It is recommended to use it.
14. Using @ to block error messages is very inefficient, extremely inefficient.
PS: Is there any alternative? If not, you still have to use it...
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.
PS: Before connecting, it is best to set the corresponding timeout mechanism, such as link timeout, read and write timeout, wait timeout, etc.
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 the speed (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 the test method) and 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 isset() Tips to speed up the execution of your code.
(Examples are as follows)
if (strlen($foo)
(Compare with the techniques 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.
PS: I have learned a lot.
30. 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.
31. Not everything must be object-oriented (OOP). Object-oriented is often very expensive, and each method and object call consumes a lot of memory.
32. It is not necessary to use classes to implement all data structures, arrays are also very useful.
33. Don’t subdivide the methods too much. Think carefully about which code you really intend to reuse?
34. You can always break the code into methods when you need it.
PS: Decomposition into methods should be appropriate. For methods with fewer lines and high frequency, try to write code directly, which can reduce function stack overhead; and method nesting should not be too deep, otherwise it will greatly affect the operating efficiency of PHP.
35. Try to use a large number of PHP built-in functions.
36. If there are a large number of time-consuming functions in the code, you can consider implementing them using C extensions.
37. 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.
38. mod_zip can be used as an Apache module to instantly compress your data and reduce data transmission volume by 80%.
39. 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. ;
PS: Remember this, try to use file_get_contents and file_put_contents, there is no need to judge whether the file handle is opened successfully.
40. Conduct file operations as little as possible, although PHP’s file operations are not inefficient;
41. Optimize the Select SQL statement and perform as few Insert and Update operations as possible (I was criticized for updating);
42. 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!);
PS: Built-in functions are nearly an order of magnitude more efficient than user-defined functions.
43. Do not declare variables inside the loop, especially large variables: objects (this seems to be not just a problem in PHP?);
PS: This is necessary. When there are too many variables or too large, the overhead of each reallocation cannot be ignored.
44. Try not to loop and nest assignments in multi-dimensional arrays;
45. Do not use regular expressions when you can use PHP’s internal string manipulation functions;
46. foreach is more efficient, try to use foreach instead of while and for loop;
47. Use single quotes instead of double quotes to quote strings;
PS: Halo, isn’t this the first one?
48. "Use i+=1 instead of i=i+1. It conforms to the habits of c/c++ and is more efficient";
49. Global variables should be unset()ed after use;