Add PHP Page To Prestashop 1.5.6

I have the need to have a php page be embedded into the framework of Prestashop.  I have followed a discussion on how to add a php page but I am still not getting it to work and there is a fatal error.

Here is my php code in /override/controllers/front called Assessment.php

<?php

class AssessmentControllerCore extends FrontController {

/**
 *  Initialize controller
 *  @see FrontController::init()
 */
public function init() {
    parent::init();
}

/**
 *  Assign template vars related to page content
 *  @see FrontController::initContent()
 */
public function initContent() {
    parent::initContent();

    $this->setTemplate(_PS_THEME_DIR_.'assessment.tpl');
}

}
?>

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Here is my .tpl file which is located in /themes/warehouse called assessment.tpl

{php}
<?php
echo "sdf";
?>
{/php}

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I am calling it in this manner http://www.abc.com/index.php?controller=Assessment and I am getting this error

[Thu Aug 17 18:03:21.105090 2017] [:error] [pid 12287] [client 69.34.35.119:57139] PHP Fatal error:  Class 'Assessment' not found in /data/web/abc.com/classes/controller/Controller.php on line 128

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Please help me get my simple php to work so that I then can add in my actual script.

Thanks,