Wordpress Ajax Json callimg

IN functions.php 

add_action('wp_footer', 'eps_footer');

function eps_footer() {

    echo "<script>var ajax_request_url = '".admin_url( 'admin-ajax.php' )."'</script>";

}

$.get( ajax_request_url,

  {

   'action' : 'get_post_title',

   'post_id' : 1

  }, function( response ){

    if ( !response.error ) {

      alert ('AJAX request made! The post title is ' + response.post_title );

    } else {

      alert ('error: ' + response.error );

    }

},  "json" );

add_action( 'wp_ajax_nopriv_get_post_title', 'get_post_title' );

add_action( 'wp_ajax_get_post_title', 'get_post_title' );

function get_post_title() {

  if ( isset($_GET['post_id']) ){

    $id = (int) $_GET['post_id'];

    $post = get_post( $id );

    header( "Content-Type: application/json" );

    echo json_encode( array('post_title' => $post->post_title) );

  } else {

    header( "Content-Type: application/json" );

    echo json_encode( array('error' => 'bad request') );

  }

  exit;

}