PHP uncaught error call to undefined function mysql_error()

    <?php if($_POST['periodicite']=="Daily")
       {
$sep="-";
 $a=$_POST['datedeb'];
$b=$_POST['datefin'];
$date1=explode($sep,$a,3);
$date2=explode($sep,$b,3);
$res1=mktime(0,0,0,$date1[1],$date1[2],$date1[0]);
 $res2=mktime(0,0,0,$date2[1],$date2[2],$date2[0]);
$r=($res2-$res1)/86400;  
      
while ($res1<=$res2) {$n=getdate($res1);
$m=$n['year']."-".$n['mon']."-".$n['mday'];

$data1 = mysqli_query($connect,"SELECT Date,Object_Name,((`sum(_Gb_mode_GPRS_attach_accept_times_)`+`sum(_Gb_mode_combined_attach_accept_times_)`)/ (`sum(_Gb_mode_GPRS_attach_request_times_)` + `sum(_Gb_mode_combined_attach_request_times_)`)) FROM Aggregation_Daily 
WHERE object_name ='$region' and date='$m'") or die(mysql_error());
        
return $data1;
$res1+=86400; 
       

while($resultat1=mysqli_fetch_array($data1,MYSQLI_ASSOC))
   echo $resultat1['2'].",";
        }}
      ?>