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SplitTestModel.php
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SplitTestModel.php
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<?php
/**
* Model for split test
*/
class SplitTestModel
{
/**
* max value could be generated by hash
*/
CONST MAX_HASH_VALUE = 4294967295;
/**
* default split variant name by experiments
*/
CONST DEFAULT_VARIANT_VALUE = 'default';
/**
* key, using for experiments
*
* @var string
*/
protected $_splitKey = '';
/**
* @var string
*/
protected $_config_path = '/path/to/config/';
/**
* @var array
*/
protected $_config = array();
/**
* result variants for user by experiments
*
* @var string
*/
protected $_splitVariants = array();
protected static $_instances = array();
/**
* @param string $key
* @return new self
*/
public static function getInstance($key = '')
{
if( empty(self::$_instances[$key]) ) {
self::$_instances[$key] = new self($key);
}
return self::$_instances[$key];
}
private function __construct( $key )
{
//by default as key use user ip
$this->_splitKey = !empty($key) ? $key : $_SERVER['REMOTE_ADDR'];
//set config
$this->_loadConfig();
}
/**
* return user variant by current experiment
*
* @param $experimentName
* @return string
*/
public function getSplitVariantByExperiment( $experimentName )
{
if( empty($this->_splitVariants[$experimentName]) ) {
$defaultVariant = self::DEFAULT_VARIANT_VALUE;
if( !empty($this->_config[$experimentName]) &&
$experimentParams = $this->_config[$experimentName]
) {
//uniform check sum of current key
$checksum = $this->_getChecksum($this->_splitKey);
//percent of max value
$percent = $checksum / self::MAX_HASH_VALUE * 100;
$totalPercent = 0;
//if isset default value in params, by default use it
if( in_array('*', $experimentParams) ) {
$defaultVariant = array_search('*', $experimentParams);
unset($experimentParams[$defaultVariant]);
}
foreach( $experimentParams as $key => $value ) {
$totalPercent += (int) $value;
if( $percent <= $totalPercent ) {
$this->_splitVariants[$experimentName] = $key;
break;
}
}
} else {
trigger_error("Experiment $experimentName doesn`t exist", E_USER_ERROR);
}
$this->_splitVariants[$experimentName] = !empty($this->_splitVariants[$experimentName])
? $this->_splitVariants[$experimentName] : $defaultVariant;
}
return $this->_splitVariants[$experimentName];
}
protected function _getChecksum($key)
{
$checksum = ( function_exists('murmurhash') ? murmurhash($key) : crc32($key) );
return $checksum < 0 ? (self::MAX_HASH_VALUE + $checksum + 1) : $checksum;
}
protected function _loadConfig()
{
if (is_file($this->_config_path))
{
$config = require($this->_config_path);
if (is_array($config))
{
$this->_config = $config;
}
}
}
}