您可以使用sql查询检查重复的用户元。在下面的代码中，如果发现其他用户的重复记录，则会显示错误消息，而不会更新值。在活动主题的函数中添加以下代码。php文件。

function save_cust_user_profile_fields( $user_id ) {

     if ( isset($_POST[\'social_number\']) ) {
        global $wpdb;
        $social_number = $_POST[\'social_number\'];
         # query to check duplicate value
        $query = "SELECT $wpdb->users.ID  FROM $wpdb->users  INNER JOIN $wpdb->usermeta ON ( $wpdb->users.ID = $wpdb->usermeta.user_id )  INNER JOIN $wpdb->usermeta AS mt1 ON ( $wpdb->users.ID = mt1.user_id ) WHERE 1=1  AND 
          ( $wpdb->usermeta.meta_key = \'social_number\' AND $wpdb->usermeta.meta_value = $social_number ) ";

        $result = $wpdb->get_results($query);
        #if result found then redirect with error msg
        if($result && $user_id != $result[0]->ID){
            add_filter( \'wp_redirect\', \'add_notice_query_variable\', 99 );
        }
        else
        {  
            # if not found duplicate then update
            update_user_meta( $user_id, \'social_number\', intval($_POST[\'social_number\']));            
        }

     }

}
add_action( \'personal_options_update\', \'save_cust_user_profile_fields\' );
add_action( \'edit_user_profile_update\', \'save_cust_user_profile_fields\' );

#Add query var in url for display error message 
function add_notice_query_variable( $location ) {
   remove_filter( \'wp_redirect\', \'add_notice_query_variable\' , 99 );
   return add_query_arg( array( \'social_number\' => $_POST[\'social_number\'] ), $location );
}

# display duplicate error admin notice
add_action( \'admin_notices\',  \'admin_notices_callback\');
function admin_notices_callback() {
   if ( ! isset( $_GET[\'social_number\'] )) {
     return;
   }
   ?>
   <div class="error notice">
      <p><?php esc_html_e( \'social_number : \'.$_GET[\'social_number\'].\' already used in other user, Please try different!\', \'\' ); ?></p>
   </div>
   <?php
  }