ajax php select,javascript - AJAX PHP function onchange select box - Stack Overflow

I have a problem about which I am very confused. I have a select box with s dynamically generated using a mysqli query:

$result = mysqli_query($db, "SELECT * FROM `users` WHERE `user_id` > 0");

echo '

Contact List';

while($row = $result->fetch_assoc()){

echo ''.$row['user_name'] . '';

}

echo '

';

I am completely new to AJAX, but I need to use jquery and ajax to pass the this.value variable to a php variable for use in a later query.

Here is my script (most of which was found online):

$("#contacts").change(function() {

//get the selected value

var selectedValue = this.value;

//make the ajax call

$.ajax({

url: 'function.php',

type: 'POST',

data: {option : selectedValue},

success: function() {

console.log("Data sent!");

}

});

});

Now, when I click a value in the select box, nothing happens. There are no warnings or errors, etc.

Please help me.

p.s. function.php does exist. It is just a simple echo for now (for testing purposes)

UPDATE: HERE IS FUNCION.PHP:

/*$val = $_REQUEST['selectedValue'];

echo $val;*/

function function(){

$val = $_REQUEST['selectedValue'];

echo $val;

}

?>

UPDATE: Thank you everyone for all your help. I have now got it to work in that the network section of chrome inspect shows the function.php being requested however I still don't get the echo (I used external .js files to get it to work). My J query function is also successful (the success function echoes into the console)