Command Center: PHP performance tips

Thursday, June 2, 2011

PHP performance tips

Category: Performance Tune, PHP — SkyHi @ Thursday, June 02, 2011

Recommended experience: Beginner to intermediate PHP knowledge
PHP is a very popular scripting language, used on many popular sites across the web. In this article, we hope to help you to improve the performance of your PHP scripts with some changes that you can make very quickly and painlessly. Please keep in mind that your own performance gains may vary greatly, depending on which version of PHP you are running, your web server environment, and the complexity of your code.

Profile your code to pinpoint bottlenecks

Hoare's dictum states that Premature optimization is the root of all evil, an important thing to keep in mind when trying to make your web sites faster. Before changing your code, you'll need to determine what is causing it to be slow. You may go through this guide, and many others on optimizing PHP, when the issue might instead be database-related or network-related. By profiling your PHP code, you can try to pinpoint bottlenecks.

Upgrade your version of PHP

The team of developers who maintain the PHP engine have made a number of significant performance improvements over the years. If your web server is still running an older version, such as PHP 3 or PHP 4, you may want to investigate upgrading before you try to optimize your code.

Use caching

Making use of a caching module, such as Memcache, or a templating system which supports caching, such as Smarty, can help to improve the performance of your website by caching database results and rendered pages.

Use output buffering

PHP uses a memory buffer to store all of the data that your script tries to print. This buffer can make your pages seem slow, because your users have to wait for the buffer to fill up before it sends them any data. Fortunately, you can make some changes that will force PHP to flush the output buffers sooner, and more often, making your site feel faster to your users.

Output Buffering Control

Avoid writing naive setters and getters

When writing classes in PHP, you can save time and speed up your scripts by working with object properties directly, rather than writing naive setters and getters. In the following example, the dog class uses the setName() and getName() methods for accessing the name property.

class dog {
  public $name = '';

  public function setName($name) {
    $this->name = $name;
  }

  public function getName() {
    return $this->name;
  }
}

Notice that setName() and getName() do nothing more than store and return the name property, respectively.

$rover = new dog();
$rover->setName('rover');
echo $rover->getName();

Setting and calling the name property directly can run up to 100% faster, as well as cutting down on development time.

$rover = new dog();
$rover->name = 'rover';
echo $rover->name;

Don't copy variables for no reason

Sometimes PHP novices attempt to make their code "cleaner" by copying predefined variables to variables with shorter names before working with them. What this actually results in is doubled memory consumption (when the variable is altered), and therefore, slow scripts. In the following example, if a user had inserted 512KB worth of characters into a textarea field. This implementation would result in nearly 1MB of memory being used.

$description = strip_tags($_POST['description']);
echo $description;

There's no reason to copy the variable above. You can simply do this operation inline and avoid the extra memory consumption:

echo strip_tags($_POST['description']);

Avoid doing SQL queries within a loop

A common mistake is placing a SQL query inside of a loop. This results in multiple round trips to the database, and significantly slower scripts. In the example below, you can change the loop to build a single SQL query and insert all of your users at once.

foreach ($userList as $user) {
  $query = 'INSERT INTO users (first_name,last_name) VALUES("' . $user['first_name'] . '", "' . $user['last_name'] . '")';
  mysql_query($query);
  }

Produces:

INSERT INTO users (first_name,last_name) VALUES("John", "Doe")

Instead of using a loop, you can combine the data into a single database query.

$userData = array();
foreach ($userList as $user) {
    $userData[] = '("' . $user['first_name'] . '", "' . $user['last_name'] . '")';
 }
$query = 'INSERT INTO users (first_name,last_name) VALUES' . implode(',', $userData);
mysql_query($query);

Produces:

INSERT INTO users (first_name,last_name) VALUES("John", "Doe"),("Jane", "Doe")...

MySQL INSERT Syntax

Additional resources

REFERENCES
http://code.google.com/speed/articles/optimizing-php.html

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