php - mysqli_num_rows() -

this question has answer here:

• reference - error mean in php? 29 answers

a part of php code doesn't work... when write code :

public $postcount = 10;   public function updates($user_ids, $lastid) {     if ($lastid == 0) {         $loadmore = '';     } else {         $loadmore = " , m.msg_id<$lastid ";     }     $db_conx = mysqli_connect("localhost", "root", "", "yusers");     $sql     = "select m.msg_id, m.uid_fk, m.message, m.created, u.fname, u.lname, m.uploads, m.profile_uid messages m, users u  m.uid_fk=u.uid , m.uid_fk in ($user_ids) $loadmore union select m.msg_id, m.uid_fk, m.message, m.created, u.fname, u.lname, m.uploads, m.profile_uid messages m, users u  m.uid_fk=u.uid , m.profile_uid in ($user_ids) $loadmore order msg_id desc limit 10" . $this->postcount;     $query   = mysqli_query($db_conx, $sql); 

i :

'warning: mysqli_fetch_array() expects parameter 1 mysqli_result, boolean given  on line 26' 

line 26 :

 while($row = mysqli_fetch_array($query, mysqli_assoc)){      //something } 

when test query :

if (!$query) { printf("error: %s\n", mysqli_error($db_conx)); exit(); } 

it gives me :

"you have error in sql syntax; check manual corresponds mysql server version right syntax use near 'msg_id desc limit10' @ line 2" 

help me please

you need put space query ends, , change order order by

$sql = "select m.msg_id, m.uid_fk, m.message, m.created, u.fname, u.lname, m.uploads, m.profile_uid messages m, users u  m.uid_fk=u.uid , m.uid_fk in ($user_ids) $loadmore union select m.msg_id, m.uid_fk, m.message, m.created, u.fname, u.lname, m.uploads, m.profile_uid messages m, users u  m.uid_fk=u.uid , m.profile_uid in ($user_ids) $loadmore order msg_id desc limit " .$this->postcount;