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เขียน PHP มาก็หลายปี พยายามปรับปรุงความรู้ตัวเองอยู่เรื่อย ๆ วันนี้ได้ Tips ในการเขียนมาเก็บไว้อีกชุดหนึ่ง ก็เอามาจากของคนอื่นแหละ ไว้ค่อยปรับเพิ่มเติมของตนเองวันหลัง

1. echo is faster than print. [Citation]
2. Wrap your string in single quotes (') instead of double quotes (") is faster because PHP searches for variables inside "..." and not in '...' , use this when you're not using variables you need evaluating in your string.  [Citation]
3. Use sprintf instead of variables contained in double quotes, it's about 10x faster. [Citation]
4. Use echo's multiple parameters (or stacked) instead of string concatenation. [Citation]
5. Use pre-calculations, set the maximum value for your for-loops before and not in the loop. ie: for ($x=0; $x < count($array); $x), this calls the count() function each time, use $max=count($array) instead before the for-loop starts. [Citation]
6. Unset or null your variables to free memory, especially large arrays. [Citation]
7. Avoid magic like __get, __set, __autoload. [Citation]
8. Use require() instead of require_once() where possible. [Citation]
9. Use full paths in includes and requires, less time spent on resolving the OS paths. [Citation]
10. require() and include() are identical in every way except require halts if the file is missing. Performance wise there is very little difference. [Citation]
11. Since PHP5, the time of when the script started executing can be found in $_SERVER[’REQUEST_TIME’], use this instead of time() or microtime(). [Citation]
12. PCRE regex is quicker than EREG, but always see if you can use quicker native functions such as strncasecmp, strpbrk and stripos instead. [Citation]
13. When parsing with XML in PHP try xml2array, which makes use of the PHP XML functions, for HTML you can try PHP's DOM document or DOM XML in PHP4. [Citation]
14. str_replace is faster than preg_replace, str_replace is best overall, however strtr is sometimes quicker with larger strings. Using array() inside str_replace is usually quicker than multiple str_replace. [Citation]
15. "else if" statements are faster than select statements aka case/switch. [Citation]
16. Error suppression with @ is very slow. [Citation]
17. To reduce bandwidth usage turn on mod_deflate in Apache v2 [Citation] or for Apache v1 try mod_gzip. [Citation]
18. Close your database connections when you're done with them. [Citation]
19. $row[’id’] is 7 times faster than $row[id], because if you don't supply quotes it has to guess which index you meant, assuming you didn't mean a constant. [Citation]
20. Use <?php ... ?> tags when declaring PHP as all other styles are depreciated, including short tags. [Citation]
21. Use strict code, avoid suppressing errors, notices and warnings thus resulting in cleaner code and less overheads. Consider having error_reporting(E_ALL) always on. [Citation]
22. PHP scripts are be served at 2-10 times slower by Apache httpd than a static page. Try to use static pages instead of server side scripts. [Citation]
23. PHP scripts (unless cached) are compiled on the fly every time you call them. Install a PHP caching product (such as memcached or eAccelerator or Turck MMCache) to typically increase performance by 25-100% by removing compile times. You can even setup eAccelerator on cPanel using EasyApache3. [Citation]
24. An alternative caching technique when you have pages that don't change too frequently is to cache the HTML output of your PHP pages. Try Smarty or Cache Lite.  [Citation]
25. Use isset where possible in replace of strlen. (ie: if (strlen($foo) < 5) { echo "Foo is too short"; } vs. if (!isset($foo{5})) { echo "Foo is too short"; } ). [Citation]
26. ++$i is faster than $ i++, so use pre-increment where possible. [Citation]
27. Make use of the countless predefined functions of PHP, don't attempt to build your own as the native ones will be far quicker; if you have very time and resource consuming functions, consider writing them as C extensions or modules. [Citation]
28. Profile your code. A profiler shows you, which parts of your code consumes how many time. The Xdebug debugger already contains a profiler. Profiling shows you the bottlenecks in overview. [Citation]
29. Document your code. [Citation]
30. Learn the difference between good and bad code. [Citation]
31. Stick to coding standards, it will make it easier for you to understand other people's code and other people will be able to understand yours. [Citation]
32. Separate code, content and presentation: keep your PHP code separate from your HTML. [Citation]
33. Don't bother using complex template systems such as Smarty, use the one that's included in PHP already, see ob_get_contents and extract, and simply pull the data from your database. [Citation]
34. Never trust variables coming from user land (such as from $_POST) use mysql_real_escape_string when using mysql, and htmlspecialchars when outputting as HTML. [Citation]
35. For security reasons never have anything that could expose information about paths, extensions and configuration, such as display_errors or phpinfo() in your webroot. [Citation]
36. Turn off register_globals (it's disabled by default for a reason!). No script at production level should need this enabled as it is a security risk. Fix any scripts that require it on, and fix any scripts that require it off using unregister_globals(). Do this now, as it's set to be removed in PHP6. [Citation]
37. Avoid using plain text when storing and evaluating passwords to avoid exposure, instead use a hash, such as an md5 hash. [Citation]
38. Use ip2long() and long2ip() to store IP addresses as integers instead of strings. [Citation]
39. You can avoid reinventing the wheel by using the PEAR project, giving you existing code of a high standard. [Citation]
40. When using header('Location: '.$url); remember to follow it with a die(); as the script continues to run even though the location has changed or avoid using it all together where possible. [Citation]
41. In OOP, if a method can be a static method, declare it static. Speed improvement is by a factor of 4. [Citation].
42. Incrementing a local variable in an OOP method is the fastest. Nearly the same as calling a local variable in a function and incrementing a global variable is 2 times slow than a local variable. [Citation]
43. Incrementing an object property (eg. $this->prop++) is 3 times slower than a local variable. [Citation]
44. Incrementing an undefined local variable is 9-10 times slower than a pre-initialized one. [Citation]
45. Just declaring a global variable without using it in a function slows things down (by about the same amount as incrementing a local var). PHP probably does a check to see if the global exists. [Citation]
46. Method invocation appears to be independent of the number of methods defined in the class because I added 10 more methods to the test class (before and after the test method) with no change in performance. [Citation]
47. Methods in derived classes run faster than ones defined in the base class. [Citation]
48. A function call with one parameter and an empty function body takes about the same time as doing 7-8 $localvar++ operations. A similar method call is of course about 15 $localvar++ operations. [Citation]
49. Not everything has to be OOP, often it is just overhead, each method and object call consumes a lot of memory. [Citation]
50. Never trust user data, escape your strings that you use in SQL queries using mysql_real_escape_string, instead of mysql_escape_string or addslashes. Also note that if magic_quotes_gpc is enabled you should use stripslashes first. [Citation]
51. Avoid the PHP mail() function header injection issue. [Citation]
52. Unset your database variables (the password at a minimum), you shouldn't need it after you make the database connection.
53. RTFM! PHP offers a fantastic manual, possibly one of the best out there, which makes it a very hands on language, providing working examples and talking in plain English. Please USE IT! [Citation]

If you still need help, try #PHP on the EFnet IRC Network. (Read the !rules first).

Also see:

• an Excellent Article about optimizing PHP by John Lim
• PEAR coding standards
• PHP best practices by ez.no (Use left and right keys to scroll through the pages)
• Tuning Apache and PHP for Speed on Unix
• Premature Optimisation
• PHP and Performance
• Performance Tuning PHP
• Develop rock-solid code in PHP
• 12 PHP optimization tips
• 10 things you (probably) didn’t know about PHP

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