Summary of some strategies for optimizing PHP program efficiency_PHP tutorial

1. 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;
2. Perform as few file operations as possible, although PHP’s file operation efficiency is not low;
3. Optimize the Select SQL statement and perform as few Insert and Update operations as possible (on update, I (Have been criticized);
4. 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!) ;
5. Do not declare variables inside loops, especially large variables: objects (this seems to be not just a problem in PHP, right?);
6. Try not to nest nested assignments in loops for multi-dimensional arrays;
7. Do not use regular expressions when you can use PHP’s internal string manipulation functions;
8. foreach is more efficient, try to use foreach instead of while and for loops;
9. Use single quotes instead of double quotes Quote the string in quotation marks;
10. "Use i =1 instead of i=i 1. It conforms to the c/c habit and is more efficient.";
11. Global variables should be unset()ed after use.
12. In multiple nested loops, if possible, the longest loop should be placed in the inner layer and the shortest loop should be placed in the outer layer. This can reduce the number of times the CPU crosses loop layers and optimize program performance.
40 Tips to Optimize Your PHP Code
1. If a method can be made static, declare it statically. The speed can be increased to 4 times.
2. echo is faster than print.
3. Use multiple parameters of echo (annotation: refers to using commas instead of periods) instead of string concatenation.
4. Determine the maximum number of loops before executing the for loop. Do not calculate the maximum value every time it loops.
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. Use the full path when including files and it will take less time to resolve the operating system path.
9. If you want to know the time when the script starts executing (annotation: the server receives the client request), using $_SERVER[‘REQUEST_TIME’] is better than time().
10. Check whether strncasecmp, strpbrk, and stripos functions can be used instead of 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 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.
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.
15. Open apache’s mod_deflate module.
16. Database connections should be closed when finished.
17. $row[‘id’] is 7 times more efficient than $row[id].
18. Error messages are expensive.
19. Try not to use functions in for loops. For example, for ($x=0; $x < count($array); $x) will call the count() function every time it loops.
20. Incrementing local variables in methods is the fastest. Almost as fast as calling local variables in a function.
21. Incrementing a global variable is 2 times slower than incrementing a local variable.
22. Incrementing an object property (eg: $this->prop++) is 3 times slower than incrementing a local variable.
23. Incrementing an undefined local variable is 9 to 10 times slower than incrementing a predefined local variable.
24. Simply defining a local variable without calling it in a function will also slow things down (to the same extent as incrementing a local variable). PHP will probably check to see if a global variable exists.
25. 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) and there was no change in performance.
26. Methods in derived classes run faster than the same methods defined in base classes.
27. 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.
28. Use single quotes instead of double quotes to enclose strings, which is faster. Because PHP will search for variables in a string surrounded by double quotes, single quotes will not. Of course, you can only do this if you don't need to include variables in the string.
29. When outputting multiple strings, use commas instead of periods to separate the strings, which is faster. Note: Only echo can do this. It is a "function" that can take multiple strings as parameters (Annotation: The PHP manual says that echo is a language structure, not a real function, so the function is enclosed in double quotes. ).
30. Apache parses a PHP script 2 to 10 times slower than parsing a static HTML page. Try to use more static HTML pages and less scripts.
31. 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.
32. 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.
33. 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() technique to speed up the execution of your code.
Ex. (Example below)
if (strlen($foo) < 5) { echo “Foo is too short”; }
vs. (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() as a language structure, meaning 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.
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 useful.
37. Don’t subdivide the methods too much. Think carefully about which code you really intend to reuse?
38. You can always break code into methods when you need to.
39. Try to use as many PHP built-in functions as possible.
40. If there are a lot of time-consuming functions in your code, you can consider implementing them as 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%.

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