Performance-wise it doesn’t matter what you use. The difference is that mysql_fetch_object returns object:
while ($row = mysql_fetch_object($result)) {
echo $row->user_id;
echo $row->fullname;
}
mysql_fetch_assoc() returns associative array:
while ($row = mysql_fetch_assoc($result)) {
echo $row["userid"];
echo $row["fullname"];
}
and mysql_fetch_array() returns array:
while ($row = mysql_fetch_array($result)) {
echo $row[0];
echo $row[1] ;
}