can't start any import : Function name must be a string

Got the same problem.

Just had the same problem. For me it turned out to be a missing custom plugin .inc file in the plugin directory. I replaced the file and it's working again.

Had same problem and same solution as #3. Upgrading feeds_tamper removed my custom plugin.

I'm having the same trouble. For me $plugin is NULL so at this point I'm not even sure what is causing the issue, I've run in to similar problems in different ways over the past couple of years.

Here's a patch that makes feeds_tamper a bit more defensive in this regard - it will just skip any plugin that doesn't define a valid callback rather than trigger a fatal error.

Yeah, I guess we could do that.

I would rather see a more helpful exception about the name of the plugin that's gone bad.

Either way, it should happen sooner in that function. There's no need to call function_exists() for every feed element.

I also reproduced this error on 7.x-1.0-beta5 (I just upgraded from 7.x-1.0-beta4) To solve the issue I added two watchdog lines and I found out that I had a tamper for a field that had no plugin specified (the missing plugin name was "Required field"). So I deleted the tamper for that field and created it again. Problem gone!

To find out the problem I added this two lines of watchdog:

$plugin = $plugins[$instance->plugin_id];
watchdog('feeds_tamper',print_r($instance,true));
watchdog('feeds_tamper',print_r($plugin,true));

A possible solution for this issue would be adding a simple "if" checking if "instance->plugin_id" is set and is not empty:

if(isset($instance->plugin_id) && !empty($instance->plugin_id)) {

          $plugin = $plugins[$instance->plugin_id];

          if ($is_array && $plugin['multi'] == 'loop') {
            foreach ($result->items[$item_key][$element_key] as &$i) {
              //plugin call as it is now
            }
          }
          elseif ($is_array && $plugin['multi'] == 'direct') {
            //plugin call as it is now
          }
          elseif (!$is_array && $plugin['single'] != 'skip') {
            //plugin call as it is now
          }
}

Let's see if this works.