WordPress $ wpdb-> get_results（）没有返回值

I'm in the process of looking at a WordPress plugin (never used WordPress before) and am running into an issue trying to execute a very basic SELECT statement against the database.

Ex:

$sql = "SELECT * FROM wp_posts";
$result = $wpdb->get_results( $sql );
var_dump($result);
echo($result);

This doesn't display anything even though my wp_posts table has a couple hundred rows. Can someone tell me what I'm missing? Thanks.

This may or may not be the issue, but often, prefixes cause trouble and it is not recommended to hardcode tables in.

Secondly, can you output the value of $wpdb? If not, and this is most likely the problem, you don't have access to $wpdb in your scope.

Use global $wpdb if you are executing this within a function.

$sql = "SELECT * FROM $wpdb->posts";
$result = $wpdb->get_results( $sql );