Several tips to improve PHP performance efficiency

The issue of how to improve efficiency is that often the same function but different code will produce very different efficiencies.

● Use single quotes instead of double quotes to enclose strings, which is 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).

● 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.
$row[’id’] is 7 times faster than $row[id].

● 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.

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

● Try to avoid using __get, __set, __autoload.

● require_once() is expensive. Try to use absolute paths when including files, because it avoids the speed of PHP searching for files in include_path, and it takes less time to parse the operating system path.

● If you want to know the time when the script starts executing (annotation: that is, the server receives the client request), using $_SERVER[‘REQUEST_TIME’] is better than time().

● Functions replace regular expressions to accomplish the same function. 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.

● 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 piece of replacement code so that each parameter passed is a character instead of just Write a line of code that accepts arrays as parameters for query and replace.
It is better to use a selective branch statement (translation annotation: switch case) than to use multiple if, else if statements.

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

● Turn on the mod_deflate module of apache to improve the browsing speed of web pages.

● The database connection should be closed when finished using it. Do not use long connections.

● Error messages are expensive.

● Incrementing local variables in methods is the fastest. Almost as fast as calling local variables in a function. Incrementing a global variable is 2 times slower than incrementing a local variable. Incrementing an object property (e.g. $this->prop ) is three times slower than incrementing a local variable. Incrementing an undefined local variable is 9 to 10 times slower than incrementing a predefined local variable. Simply defining a local variable without calling it in a function also slows things down (to the same extent as incrementing a local variable). PHP will probably check to see if a global variable exists.

● 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. Methods in a derived class run faster than the same method defined in a base class. Calling an empty function with one argument takes as long as incrementing the local variable 7 to 8 times. A similar method call takes close to 15 local variable increment operations.

● 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. 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.

● 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.

● When operating a string and need to check whether its length meets certain requirements, you will naturally use the strlen() function. This function executes fairly quickly because it doesn't 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.

● 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.

● Everything does not have to be object-oriented (OOP). Object-oriented is often very expensive, and each method and object call consumes a lot of memory.
It is not necessary to use classes to implement all data structures, arrays are also useful.

● Don’t break down the methods too much. Think carefully about which code you really intend to reuse? You can always break the code into methods when you need to.

● Try to use a large number of PHP built-in functions. If there are a lot of time-consuming functions in your code, you might consider implementing them as C extensions. 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.

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

● 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! However, you should pay attention to the PHP version problem of file_get_contents when opening a URL file;

● Try to perform as few file operations as possible, although PHP's file operation efficiency is not low;

● Optimize Select SQL statement, perform as few Insert and Update operations as possible;

● Use PHP internal functions as much as possible;

● Do not declare variables inside the loop, especially large variables: objects ;

●Try not to loop nested assignments for multi-dimensional arrays;

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

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

●"Use i =1 instead of i=i 1. It conforms to the c/c habit and is more efficient";

● Global variables should be unset()ed after use;

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