使用AJAX jQuery的基本Qn？

I just started learning using AJAX with Codeigniter. On my view, I have a textarea and a button which uses AJAX to submit the text in the textarea to my controller, which retrieves data from the database and returns this data to the view. However I am getting the error "disallowed key characters" in the callback function. This happens even when I simply echo a string. What is happening?

Btw, should I use return $result or echo $result in the controller to pass the data back to the webpage?

AJAX

$(function() {
    $("#search_button").click(function(e){
        e.preventDefault();
        var search_location = $("#search_location").val();
        $.get('index.php/main/get_places', search_location, function(data){
            $("#result").html(data);
            console.log(data);
    });
});

});

Controller

function get_places($address) {

    $search_latlng = $this->geocode_address($address);
    $this->load->model('main_model.php');
    $result = $this->main_model->get_places($search_latlng);

    echo "test";
}

CodeIgniter has restricted the characters in the url to:

$config['permitted_uri_chars'] = 'a-z 0-9~%.:_\-'; //Inside config.php

Chances are you are putting in characters that not in this list in the address when you send the AJAX request. My suggestion would be change the $.get to $.post and then get the post data out in the controller. Something like this:

AJAX

$(function() {
    $("#search_button").click(function(e){
        e.preventDefault();
        var search_location = $("#search_location").val();
        $.post('index.php/main/get_places', {'search_location': search_location}, function(data){
            $("#result").html(data);
            console.log(data);
        });
    });
});

Controller

function get_places() {
    $address = $this->input->post('search_location');
    $search_latlng = $this->geocode_address($address);
    $this->load->model('main_model.php');
    $result = $this->main_model->get_places($search_latlng);

    echo $result;
}

As for the echo vs return, use echo.

You're probably not allowing querystrings in your URL and the Ajax function adds querystring to the url. Take a look at the following url to learn how to turn querystrings on:

http://www.askaboutphp.com/58/codeigniter-mixing-segment-based-url-with-querystrings.html