使用get_user_meta时WP中导致此错误的原因是什么？

Question

I'm adding additional metadata to users in WordPress and every time I use get_user_meta I'm getting this error: Notice: Object of class WP_User could not be converted to int in /.../wp-includes/functions.php on line 2999

My code is

foreach( $metadata as $key => $value ) {

        if ( !get_user_meta( $wcm_users[$i], $key, '' ) ) {

            add_user_meta( $wcm_users[$i]->ID, $key, '' );

        }

    }

$metadata is an array of additional metadata I want to add, so its a basic check to see if the metadata is already added, if not, add in. Can't understand what's triggering the error. If I remove the get_user_meta the error goes away.

Any ideas of what is going on?

Answer 1

get_user_meta() takes an integer ID. You're passing it a WP_User object. Try:

    foreach( $metadata as $key => $value ) {

        if ( !get_user_meta( $wcm_users[$i]->ID, $key, '' ) ) {

            add_user_meta( $wcm_users[$i]->ID, $key, '' );

        }

    }

Also, note that the third (optional) parameter to get_user_meta() is a boolean to indicate if you want to treat the value as a single value or an array—I'm guessing you should just be leaving it off to get the default behaviour of a single value. That's what the empty string you're passing will be doing (as an empty string is a boolean false) but it's not that obvious from your code.

Also, update_user_meta() will add the meta if it doesn't exist, and update it if it does, which is what you say you want to do, so:

foreach( $metadata as $key => $value ) {
    update_user_meta( $wcm_users[$i]->ID, $key, '' );
}

...will probably do what you want, anyway.