Fatal Error: Undefined Function in stand alone PHP script

Hi everyone. I would like to be able to track a user’s preference for sounds on the website. The preference has to be available from page load to page load.

I added an option to the funtions.php script

add_option('audio_toggle','on','','yes');

Next, I created a stand alone php script (raven-functions.php) to update or get a user defined option.

<?php
/** =================================
 *  AUDIO FUNCTIONS
 * ================================== */

    	if(isset($_POST['action']) && !empty($_POST['action'])) {
        	$action = $_POST['action'];
        	switch($action) {
        		case 'get_audio_toggle' :
            			get_audio_toggle();
		            	break;
        		case 'set_audio_toggle' :
		            	set_audio_toggle();
            			break;
        	}
    	}

	function get_audio_toggle() {
		echo get_option('audio_toggle');
	}
	add_action('get_option', 'get_audio_toggle');

	function set_audio_toggle() {
		if(isset($_POST['new_value']) && !empty($_POST['new_value'])) {
			$new_value = $_POST['new_value'];
			update_option('audio_toggle', $new_vlaue);
			echo get_option('audio_toggle');
		}
	}
	add_action('update_option', 'set_audio_toggle');
?>

Finally, I created a javascript that would respond to the user clicking a ‘speaker’ image on or off on the webpage. The function in the javascript calls the both PHP functions using AJAX.

//==========================================================
//  AUDIO FUNCTIONS
//==========================================================
//--------------------------------------
  function toggleAudio() {
//-------------------------------------- 

    $.get("/wordpress/wp-content/themes/LCARS/raven_functions.php", {action:'get_audio_toggle'}, function(response, status) {
        if (status === "success") {
            var myAudio = document.getElementById("raven-audio");
            var toggle = "";
            if(response === "off") {
                $('#raven-audio-image').css('background','url(/wordpress/wp-content/themes/LCARS/images/raven-audio-on-000.png)');
                $('#raven-audio-image').prop('title','click to turn audio off');
                myAudio.play();
                toggle = "on";
            }
            else {
                $('#raven-audio-image').css('background','url(/wordpress/wp-content/themes/LCARS/images/raven-audio-off-000.png)');
                $('#raven-audio-image').prop('title','click to turn audio on');
                myAudio.pause();
                myAudio.currentTime = 0;
                toggle = "off";
            }
            $.post("/wordpress/wp-content/themes/LCARS/raven_functions.php", {action:'set_audio_toggle', new_value:toggle});
        }
    });
  }

When I click the image button on the webpage, I am getting the following error message, “fatal error: undefined function update_option() in the php file at line 27. I am new to wordpress and read through documentation and searched for a solution. I alsso made sure that the option.php script was included as a required in the wp-settings.php file.

I would appreciate if someone could help point me in the right direction to resolving what should be a simple requirement.

Thank you,
Jim Von Dolteren