Wordpress自定义短代码 - >如果没有参数则不显示

Question

A simple wordpress shortcode function gets the querystring key => value pair from the URL and outputs the value onto the page where the shortcode is placed. I set the parameter in the shortcode to determine which key to call e.g. [urlparam param="username"].

Unfortunately, if there is no querystring or if the querystring key is not present then the raw shortcode displays on the page rather than rendering any result or displaying nothing. How would I edit the shortcode function so that nothing displays if there is no querystring or if the key being looked for is not there?

function urlparam_function( $atts ) {  
    extract( shortcode_atts( array(
        'param' => 'param',
    ), $atts ) );
    return $_GET[$param];
}
add_shortcode('urlparam', 'urlparam_function');

Answer 1

remove $_GET use only $param like below:

function urlparam_function( $atts ) {  
    extract( shortcode_atts( array(
        'param' => 'param',
    ), $atts ) );
    return $param;
}
add_shortcode('urlparam', 'urlparam_function');