Shortcode custom query not passing value

Question

I have created a shortcode to show custom single custom post type to another post. Here is the code:

function clients_shortcode(){

    $output = '';
    //Attributes
    $defaults = array(
        'c_name'        => '',
        'c_session' => ''
    );

    $atts = shortcode_atts($defaults, $atts);
    $name = $atts['c_name'];
    $session = $atts['c_session'];

    $args = array(

        'post_type'     => 'client',
        'meta_query'    => array(
            'relation'      => 'AND',
            array(
                'key'       => 'client_name',
                'value'     => $name,
                'compare'   => '='  
            ),
            array(
                'key'       => 'session_number',
                'value'     => $session,
                'compare'   => '='
            )
        )

    );

    $client_sess = new WP_Query ($args);

    if($client_sess->have_posts()): while($client_sess->have_posts()): $client_sess -> the_post();

    $output .= '<h1>' . get_the_title() . '</h1>';
    $output .= '<div>' . get_field('session_hypnosis') . '</div>';
    $output .= '<div>' . get_field('session_video') . '</div>';

    endwhile;
    endif;
    wp_reset_query();

    return $output;
}

add_shortcode('clients', 'clients_shortcode');

The output is showing nothing but if I change the code to static like this

$args = array(
        'post_type'     => 'client',
        'meta_query'    => array(
            'relation'      => 'AND',
            array(
                'key'       => 'client_name',
                'value'     => 'Nayan',
                'compare'   => '='  
            ),
            array(
                'key'       => 'session_number',
                'value'     => 1,
                'compare'   => '='
            )
        )

    );

The shortcode then show the post for client Nayan and session 1. But when I am passing arguments to the shortcode, it is not working.

NOTE: I am using ACF to generate custom fields.

Thanks In Advance

Answer 1

You haven't defined $atts, so your function isn't receiving any of the attributes passed by the user. This isn't sufficient:

$atts = shortcode_atts($defaults, $atts);

That just combines $atts and $defaults into $atts, but the original $atts hasn't been defined. You need to accept $atts as the first argument passed to your function:

function clients_shortcode( $atts ) {