PHP code optimization knowledge sharing

This article mainly shares with you some knowledge about php code optimization. The article summarizes more than 40 knowledge points about optimizing code, hoping to help everyone.

1. Don’t just copy variables

BAD:
$description = $_POST['description'];
echo $description;
GOOD:
echo $_POST['description'];

2. Use single quotes for strings
3. Use switch/case instead of if/else
4. Turn on the mod_deflate module of apache to improve the browsing speed of web pages.
5. The database connection should be closed when finished using it. Do not use long connections.
Optimize PHP generation
1. If a method can be static, declare it as static, and the speed can be increased by 1/4;
2. Echo is more efficient than print, because echo has no return value , print returns an integer;
3. Set the maximum number of loops before the loop, not during the loop; it is best to use foreach instead
4. Destroy variables to release memory, especially large arrays; unset(), null
5. Avoid using magic methods like __get, __set, __autoload, etc.;
6.require_once(), include_once() are more resource-consuming, require() has higher execution efficiency;*
7. Use absolute paths in includes and requires, so you spend less time analyzing paths;
8. If you need to get the time from sexinsex to script execution, $_SERVER['REQUSET_TIME'] is better than time( );
9. If you can use character processing functions, try to use them, because the efficiency is higher than regular expressions;
10. str_replace character replacement is faster than regular replacement preg_replace, but strtr is 1/4 faster than str_replace;
11. If a function can accept both arrays and simple characters as parameters, such as character replacement, and the parameter list is not too long, you can consider using more concise replacement statements to replace only one character at a time,
instead of Accepts arrays as search and replace parameters. Make big things small, 1+1>2;
12. Covering errors with @ will reduce the running speed of the script;
13.$row['id'] is 7 times faster than $row[id], it is recommended to keep it The habit of adding quotes to array keys;
14. Error messages are very useful;
15. Don’t use functions in loops, such as For($x=0; $x < count($array); $x ), the count() function calculates first outside;*
16. Creating local variables in a method is the fastest, 97xxoo is almost as fast as calling local variables in a method;
17. Creating a global variable is faster than Local variables are 2 times slower;
18. Creating an object property (variable in a class) such as ($this->prop++) is 3 times slower than local variables;
19. Creating an undeclared local Variables are 9-10 times slower than an initialized local variable;
20. Declaring a global variable that has not been used by any function will also reduce performance (as well as declaring the same number of local variables), and PHP may Check whether this global variable exists;
21. The performance of the method has nothing to do with the number of methods defined in a class, because I added 10 or more methods to the tested class (these methods are before and after the test method ); there is no difference in performance;
22. The performance of methods in subclasses is better than that in base classes;
23. The time it takes to run a function that calls only one parameter and has an empty function body is equal to 7-8 times $localvar++ operation, and a similar method (function in the class) runs equal to about 15 $localvar++ operations;
24. Single quotes are stronger than double quotes when defining a string
25. When outputting a string, use It is faster to use commas instead of dots. Note: This only works for echo. This function can accept some strings as parameters;
26. In the apache server, a PHP script page takes at least 2-10 times longer to generate than the corresponding HTML static page. It is recommended to use more static HTML pages and a small number of scripts;
27. Unless you have a cache installed, your php script needs to be recompiled every time it is accessed. It is recommended to install a PHP cache program, which can significantly improve your performance by 20-100% by removing some repeated compilation;
28. It is recommended to use memcached, a high-performance distributed memory object caching system, to improve dynamic network applications Program performance, reduce the burden on the database;
29. Use the ip2long() and long2ip() functions to convert the IP address into an integer type and store it in the database instead of a character type. This reduces storage space by almost 1/4. At the same time, addresses can be easily sorted and searched quickly;
30. 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;
31. If you are using php5 and mysql4.1 or above, consider using the improved function mysqli_* of mysql_*;
32. Try to use the ternary operator (?:);
33. You want to see if PEAR has what you need before completely redoing your project. PEAR is a huge resource library, as many PHP developers know;
34. Use highlight_file() to automatically print a well-formatted copy of the page source code;
35. Use the error_reporting(0) function to prevent potentially sensitive information from being displayed to users. Ideally error reporting should be completely disabled in the php.ini file. But if you are using a shared virtual host and you cannot modify
php.ini, then 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 it ) This can effectively protect sensitive SQL queries and paths from being displayed when errors occur;
36. Use gzcompress() and gzuncompress() to compress (decompress) large-capacity strings before storing (retrieving) them from the database hour. This built-in function can be compressed to 90% using the gzip algorithm;
37. A function can have multiple return values ​​by referencing the parameter variable address. You can add an "&" before the variable to indicate passing it by address rather than by value;
38.Fully understand “magic quotes” and the dangers of SQL injection. I'm hoping that most developers reading this are already familiar with SQL injection.
However, I list it here because it's absolutely critical to understand. If you' ve never heard the term before, spend the entire rest of the day googling
and reading.
39. Using strlen() is not very fast because it needs to call some other operations such as lowercase and hash table queries. We can Use isset() to achieve similar functions. isset() is faster than strlen();
40. Regarding incrementing $i++ or decrementing $i-- will be slightly slower than ++$i or --$i. This is It is unique to PHP and is not suitable for other languages.
42. The foreach loop replaces while or for *
43. Use file_get_contents() for large files, and fopen(), fread() for small files.
44. Normal writing method It is faster than encapsulating methods and classes
VLD tool to view Opcode


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