Symphony.

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    /**
     * Convenience function to add a `<script>` element to the `$this->_head`. By default
     * the function will allow duplicates to be added to the `$this->_head`. A duplicate
     * is determined by if the `$path` is unique.
     *
     * @param string $path
     *  The path to the script file
     * @param integer $position
     *  The desired position that the resulting XMLElement will be placed
     *  in the `$this->_head`. Defaults to null which will append to the end.
     * @param boolean $duplicate
     *  When set to false the function will only add the script if it doesn't
     *  already exist. Defaults to true which allows duplicates.
     * @return integer
     *  Returns the position that the script has been set in the `$this->_head`
     */
    public function addScriptToHead($path, $position = null, $duplicate = true){
        if($duplicate === true || ($duplicate === false && $this->checkElementsInHead($path, 'src') === false)){
            $script = new XMLElement('script');
            $script->setSelfClosingTag(false);
            $script->setAttributeArray(array('type' => 'text/javascript', 'src' => $path));

            return $this->addElementToHead($script, $position);
        }
    }