40 examples of efficient writing in PHP

0. It is quicker to use single quotes instead of double quotes to contain strings. Because PHP searches for variables in a string enclosed in double quotes, single quotes are not, note: only echo can do this, it is a "function" that can take multiple strings as arguments: ECHO is the language structure, not the real function, so the function is added double quotes.
1, if you can define the method of the class as static, as far as possible to define static, it will increase the speed of nearly 4 times times.

2, $row [' ID '] speed is $row[id] 7 times times.

3, ECHO is faster than print, and uses Echo's multiple arguments (to refer to a comma rather than a period) instead of a string connection, such as Echo $str 1, $str 2.

4. It is best to use foreach to execute the loop, determine the maximum number of loops before executing the For loop, and do not compute the maximum value for Each loop.

5, the cancellation of those unused variables, especially large arrays, in order to free memory.

6, try to avoid the use of __get,__set,__autoload. The functions that begin with __ are named Magic Functions, which are in the kitchen for specific conditions. In total, there are a few magic functions

__construct (), __destruct (), __get (), __set (), __unset (), __call (), __callstatic (), __sleep (), __wakeup (), __tostring () , __set_state (), __clone (), __autoload ()

7, require_once () costly.

8, include files as far as possible using the absolute path, because it avoids the PHP to include_path to find the file speed, parsing the operating system path requires less time.

9, if you want to know the script to start execution (that is, the server to receive client requests) at the moment, using $_server[' request_time ' is better than time ().

10. Functions do the same function instead of regular expressions.

11, the Str_replace function is faster than the Preg_replace function, but the efficiency of the STRTR function is four times times that of the Str_replace function.

12. If a string substitution function can accept an array or character as a parameter, and the parameter length is not too long, consider writing an extra paragraph of substitution code so that each pass parameter is a character, rather than writing a single line of code to accept the array as a query and replacement parameter.

13, using the SELECT Branch statement instead of the conditional statement, select the branch statement (that is, switch case) better than using multiple if,else if statements.

14, without @, using the @ block error message is very inefficient, extremely inefficient.

15, open the Apache mod_deflate module, you can improve the browsing speed of the Web page.

16, the database connection should be turned off when use is finished, do not use long connection.

17. Error messages are costly.

18, in the method to increase the local variable, speed is the fastest. Almost as fast as calling a local variable in a function.

19, incrementing a global variable is twice times slower than incrementing a local variable.

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

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

22. Defining only one local variable instead of calling it in a function also slows down the speed (which is equivalent to incrementing a local variable). PHP will probably check to see if there are any global variables.

23. The method call appears to have nothing to do with the number of methods defined in the class, because I added 10 methods (both before and after the test method), but there was no change in performance.

24. Methods in a derived class run faster than the same method defined in the base class.

25. Call an empty function with one parameter, which takes as much time as 7 to 8 local variable increment operations. A similar method invocation takes approximately 15 times of local variable increments.

26, the time of Apache parsing a PHP script is 2 to 10 times times slower than parsing a static HTML page. Use static HTML pages as much as possible and use less scripting.

27. Unless the script can be cached, it will be recompiled every time it is invoked. The introduction of a set of PHP caching mechanisms typically increases performance from 25% to 100% to exempt compilation overhead.

28, try to do the cache, you can use memcached. Memcached is a high-performance memory object caching system that can be used to speed up dynamic Web applications and reduce database load. It is useful to cache the operation Code (OP code) so that the script does not have to recompile for each request.

29. When manipulating strings and having to check whether their lengths meet certain requirements, you will of course use the strlen () function. This function executes fairly quickly because it does not do any calculations and returns only the known string lengths stored in the Zval structure (c's built-in data structure for storing PHP variables). However, since strlen () is a function, it will be somewhat slower, because function calls go through a number of steps, such as lowercase letters, PHP is case-insensitive, and hash lookups follow the functions that are called. In some cases, you can use the isset () technique to speed up the execution of your code.

(Examples below)

if (strlen ($foo) < 5) {echo "Foo is too Short" $$}
(compare with the following tips)
if (!isset ($foo {5})) {echo "Foo is too Short" $$}

Calling Isset () happens to be faster than strlen (), because unlike the latter, Isset () as a language structure means that its execution does not require function lookup and lowercase. That is, you're actually not spending too much on the top-level code that verifies the length of the string.

34, when the execution variable $i increment or decrement, $i + + will be slower than the + + $i. This difference is specific to PHP and does not apply to other languages, so please do not modify your C or Java code and expect them to quickly become useless. + + $i faster because it requires only 3 instructions (opcodes), $i + + requires 4 instructions. A post increment actually produces a temporary variable, which is then incremented. And the predecessor increment increases directly on the original value. This is one of the most optimized processes, as Zend's PHP optimizer has done. Keeping this optimization in mind is a good idea, because not all command optimizer will do the same optimization, and there are a large number of Internet service providers (ISPs) and servers that do not have assembly instruction optimizer.

35, is not a matter of object-oriented (OOP), object-oriented often expensive, each method and object calls will consume a lot of memory.

36, not to use the class to implement all the data structure, the array is also useful.

37, do not subdivide the method too much, carefully think about what you really intend to reuse the code?

38, when you need, you can always break down the code into a method.

39, try to use a large number of PHP built-in letters