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Thread: Some PHP Tips

  1. #1
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    Lightbulb Some PHP Tips

    For information about what PHP is, when/why you should use it, or how to get started, see this:
    http://dynamicdrive.com/forums/showthread.php?t=25847

    ------------------------------
    General tips for coding with PHP:

    1. If a method can be static‚ declare it static. Speed improvement is by a factor of 4.
    2. echo is faster than print.
    3. Use echo’s multiple parameters instead of string concatenation.
    4. Set the maxvalue for your for-loops before and not in the loop.
    5. Unset your variables to free memory‚ especially large arrays.
    6. Avoid magic like __get‚ __set‚ __autoload
    7. require_once() is expensive
    8. Use full paths in includes and requires‚ less time spent on resolving the OS paths.
    9. If you need to find out the time when the script started executing‚ $_SERVER[’REQUEST_TIME’] is preferred to time()
    10. See if you can use strncasecmp‚ strpbrk and stripos instead of regex
    11. str_replace is faster than preg_replace‚ but strtr is faster than str_replace by a factor of 4
    12. If the function‚ such as string replacement function‚ accepts both arrays and single characters as arguments‚ and if your argument list is not too long‚ consider writing a few redundant replacement statements‚ passing one character at a time‚ instead of one line of code that accepts arrays as search and replace arguments.
    13. It’s better to use select statements than multi if‚ else if‚ statements.
    14. Error suppression with @ is very slow.
    15. Turn on apache’s mod_deflate
    16. Close your database connections when you’re done with them
    17. $row[’id’] is 7 times faster than $row[id]
    18. Error messages are expensive
    19. Do not use functions inside of for loop‚ such as for ($x=0; $x < count($array); $x) The count() function gets called each time.
    20. Incrementing a local variable in a method is the fastest. Nearly the same as calling a local variable in a function.
    21. Incrementing a global variable is 2 times slow than a local var.
    22. Incrementing an object property (eg. $this->prop++) is 3 times slower than a local variable.
    23. Incrementing an undefined local variable is 9-10 times slower than a pre-initialized one.
    24. Just declaring a global variable without using it in a function also slows things down (by about the same amount as incrementing a local var). PHP probably does a check to see if the global exists.
    25. 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.
    26. Methods in derived classes run faster than ones defined in the base class.
    27. 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.
    28. Surrounding your string by ’ instead of " will make things interpret a little faster since php looks for variables inside "..." but not inside ’...’. Of course you can only do this when you don’t need to have variables in the string.
    29. When echoing strings it’s faster to separate them by comma instead of dot. Note: This only works with echo‚ which is a function that can take several strings as arguments.
    30. A PHP script will be served at least 2-10 times slower than a static HTML page by Apache. Try to use more static HTML pages and fewer scripts.
    31. Your PHP scripts are recompiled every time unless the scripts are cached. Install a PHP caching product to typically increase performance by 25-100% by removing compile times.
    32. Cache as much as possible. Use memcached - memcached is a high-performance memory object caching system intended to speed up dynamic web applications by alleviating database load. OP code caches are useful so that your script does not have to be compiled on every request
    33. When working with strings and you need to check that the string is either of a certain length you’d understandably would want to use the strlen() function. This function is pretty quick since it’s operation does not perform any calculation but merely return the already known length of a string available in the zval structure (internal C struct used to store variables in PHP). However because strlen() is a function it is still somewhat slow because the function call requires several operations such as lowercase & hashtable lookup followed by the execution of said function. In some instance you can improve the speed of your code by using an isset() trick.

      Ex.
      if (strlen($foo) < 5) { echo "Foo is too short"; }
      vs.
      if (!isset($foo{5})) { echo "Foo is too short"; }


      Calling isset() happens to be faster then strlen() because unlike strlen()‚ isset() is a language construct and not a function meaning that it’s execution does not require function lookups and lowercase. This means you have virtually no overhead on top of the actual code that determines the string’s length.

      [*When incrementing or decrementing the value of the variable $i++ happens to be a tad slower then ++$i. This is something PHP specific and does not apply to other languages‚ so don’t go modifying your C or Java code thinking it’ll suddenly become faster‚ it won’t. ++$i happens to be faster in PHP because instead of 4 opcodes used for $i++ you only need 3. Post incrementation actually causes in the creation of a temporary var that is then incremented. While pre-incrementation increases the original value directly. This is one of the optimization that opcode optimized like Zend’s PHP optimizer. It is a still a good idea to keep in mind since not all opcode optimizers perform this optimization and there are plenty of ISPs and servers running without an opcode optimizer.
    34. Not everything has to be OOP‚ often it is too much overhead‚ each method and object call consumes a lot of memory.
    35. Do not implement every data structure as a class‚ arrays are useful‚ too
    36. Don’t split methods too much‚ think‚ which code you will really re-use
      You can always split the code of a method later‚ when needed
    37. Make use of the countless predefined functions
    38. If you have very time consuming functions in your code‚ consider writing them as C extensions.
    39. 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
    40. mod_gzip which is available as an Apache module compresses your data on the fly and can reduce the data to transfer up to 80%
    Last edited by djr33; 12-31-2009 at 08:58 PM. Reason: added link to main FAQ

  2. #2
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    Can you cite where you got this information from?

    You also should explain items like #17, where PHP novices would most likely not know the difference.

  3. #3
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    Close your database connections when you’re done with them.
    I don't do this usually. Why should I? Is it faster??

  4. #4
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    mysql connections are automatically closed when the script stops running.
    If you can manually close them, it's better because:
    1. It's faster: free up a system resource for both the php script and the mysql connection.
    2. It's slightly more secure: once the connection is closed, something funny can't happen with injection of code... but then again, the odds of this happening if you're no longer using mysql queries is low.
    3. It's also clearer: if you close it, and you end up using different connections later, then you don't have to worry about which one is currently open.

    However, none of these reasons convince me to do it, mostly because there are frequently so many different instances of mysql queries in my scripts (many in layered includes) that I wouldn't even know when to close it-- is that the last one, or will there be another in the next include?

    This applies more if you have a script with an organization/computational section at the top then a template for outputting the data in the end: by the end you should have all your queries completed, so you can close the connection and make things simpler while executing the template and outputting data.

    In the end, if you are just closing the mysql queries as the last action in your script, it's basically useless. If you are able to do it halfway through the execution, it may be helpful.


    The only exception to this is if you are using a persistent mysql connection (it wouldn't be by accident) and that MUST be closed when you're done with it, because it will persist-- not be closed automatically.
    Last edited by djr33; 01-01-2014 at 04:23 AM.
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