Function name must be a string fatal error

I have this Fatal error, I've been staring at my code for hours.. I think it has nothing to do with the name of the function action_send, it must be some silly 'missing parenthesis' or something...

can you help me please ?

if (...) {}
else if (!historic_exist($id)) {
                action_send($req, '0', (strpos($req['TAG'], 'ADMD') !== false) ? $req['ID_ACT'] : '');
//the error is in this line : 
                    if ((strpos($req['WF'],'Install') !== false) && $req('ID_EQU') !== '')
                action_send($req, '', '0');
                    }

via Chebli Mohamed