this function returns FALSE when you have an error in your syntax in one of your queries, so be carefull with this type of construction when tracking errors:

<?php

//error in the second sub query  
$result = $db->multi_query("select * from news; seleeeeeeect id from news; update news set title='new title' where id= 12 ");

//code inside object class
$this->_db = new Mysqli($host, $user, $password, $database, $port, $socket);
        
do {
    $result = $this->_db->store_result();
    $this->_resultMulti[] = $result;
    $this->_errnoMulti[] = $this->_db->errno;

    if(is_object($result)) {
        $result->free_result();
    }
                
} while($this->_db->next_result());

?>

in this construction all you have in the $this->_errnoMulti is :

array(1) {
  [0]=>
  int(0)
}
 
which means that there are no errors if you are not checking how many queries are executed!

Stored procedures few rowset example:

some_file.php
<?php
function proc() {
  global $global;
  $db_connect_list = array('site');
  SQLinit($db_connect_list);
  if(isset($global['error'])){return;}
  SQL('CALL `procedure`();');
  while($row=mysqli_fetch_assoc($global['result'])){
    // do some
  }
  SQLnext();
  while($row=mysqli_fetch_assoc($global['result'])){
    // do some
  }
  SQLnext();
  while($row=mysqli_fetch_assoc($global['result'])){
    // do some
  }
  SQLclose($db_connect_list);
}
?>

config.php
<?php
  $global['sys']['db']['site'] = array('host'=>'localhost', 'user'=>'site', 'pass'=>'');
?>

engine.php
<?php
function SQLinit($array_list){
  global $global;
  foreach($array_list as $set){
    if(!$global['sys']['db'][$set]['connect'] = mysqli_connect(
        $global['sys']['db'][$set]['host'],
        $global['sys']['db'][$set]['user'],
        $global['sys']['db'][$set]['pass'])){
      $global['error']['code'] = 500;
      $global['error']['text'] = 'Database not avaliable';
      $w=fopen('error.log','a+');
      fwrite($w,'time: '.date('Y M d H:i:s')."\r\n");
      fwrite($w,'errno: '.mysqli_connect_errno()."\r\n");
      fwrite($w,'error: '.mysqli_connect_error()."\r\n");
      fclose($w);
      return;
    }
    if(!isset($global['sys']['default_connect']))
      $global['sys']['default_connect'] = $global['sys']['db'][$set]['connect'];
    SQL('SET NAMES \'utf8\' COLLATE \'utf8_unicode_ci\';', $global['sys']['db'][$set]['connect']);
    SQL('SET CHARACTER SET \'utf8\';', $global['sys']['db'][$set]['connect']);
    SQL('SET character_set_connection = \'utf8\';', $global['sys']['db'][$set]['connect']);
  }
}
function mTime(){
  list($usec, $sec) = explode(" ", microtime());
  return ((float)$usec+(float)$sec);
}
function SQL($sql, $connect = -1){
  global $global;
  if($connect === -1)$connect = $global['sys']['default_connect'];
  if(isset($global['error']['sql']))return;
  while ($connect->next_result()) $connect->store_result();
  $begin=mTime();
  $global['result']=mysqli_query($connect, $sql);
  $end=mTime();
  $global['sys']['time_sql']+=$end-$begin;
  $error=mysqli_error($connect);
  if($error!=''){
    $global['error']['code'] = 502;
    $global['error']['text'] = 'SQL error';
    $global['error']['sql'] = true;
    $w=fopen('error.log','a+');
    fwrite($w,'time: '.date('Y M d H:i:s')."\r\n");
    fwrite($w,'errno: '.mysqli_errno($connect)."\r\n");
    fwrite($w,'error: '.$error."\r\n");
    fwrite($w,'sql: '.$sql."\r\n");
    fclose($w);
  }else{
    $w=fopen('sql.log','a+');
    fwrite($w,'time: '.date('Y M d H:i:s')."\r\n");
    fwrite($w,'sql: '.$sql."\r\n");
    fclose($w);
  }
}

function SQLnext($connect = -1){
  global $global;
  if($connect === -1)$connect = $global['sys']['default_connect'];
  if(isset($global['error']['sql']))return;
  $connect->next_result();
  $global['result'] = $connect->store_result();
}

function SQLclose($array_list){
  global $global;
  foreach($array_list as $set){
    mysqli_close($global['sys']['db'][$set]['connect']);
  }
}
?>