Our current framework is heavily using a "Factory" to instantiate classes on the fly. It used ReflectionClass::newInstanceArgs() for classes with arguments. Since Reflection is quite slow it decreased our performance. The gist shows a solution that is less beautiful but more performant.

gistfile1.php

<?php

class Factory
{
    
    // ...
    
    /**
     * Helper to instantiate objects with dynamic constructors.
     *
     * The beautiful way:
     * <code>
     * $reflection = new ReflectionClass($classNameNormalized);
     * return $reflection->newInstanceArgs($arguments);
     * </code>
     *
     * Reflection->newInstanceArgs() is very slow and therefore replaced
     * by generated PHP code which is executed with eval.
     *
     * @param string $class
     * @param array $arguments
     * @return mixed
     */
    public static function createInstance($class, $arguments = null)
    {
        if (is_null($arguments)) {
            return new $class;
        }

        $instance = null;
        $codeScaffold = '$instance = new %s(%s);';
        $codeArguments = array();

        foreach ($arguments as $index => $argument) {
            ${'arg' . $index} = $argument;
            $codeArguments[] = '$arg' . $index;
        }

        eval(sprintf($codeScaffold, $class, implode(', ', $codeArguments)));

        return $instance;
    }
}