When push objects to array in php, all objects are same

Try to declare $o first (inside the while loop):

$o = new stdClass;

That's because you are pushing the same object into the array each time.

You should push a new object in each iteration instead. For example, if $o is a stdClass object, use $o = new stdClass inside the loop:

while($row=mysql_fetch_assoc($result))
{
    $o = new stdClass;
    $o->pw=$row['password'];
    $o->mail=$row['mail'];
    array_push($arr, $o);
}

You can also use mysql_fetch_object, which is perhaps more appropriate:

while($o=mysql_fetch_object($result))
{
    array_push($arr, $o);
}

The properties on the above object will be named based on your SQL query columns, so to achieve the same effect you would also need to change the query to select password AS pw, mail from account.

Finally, another option is to clone the object each time -- although the other alternatives are almost always preferable:

while($row=mysql_fetch_assoc($result))
{
    $o = clone $o;
    $o->pw=$row['password'];
    $o->mail=$row['mail'];
    array_push($arr, $o);
}

This is because the object is being added to the array as a reference. Each element in the array is a reference to an object, the same object.

You didn't declare $o, so when you first do $o->pw, PHP creates an object for you. When it does this, it creates it outside the scope of the loop, so each iteration of the loop refers to the same $o.

You need to declare $o each loop iteration.

while($row=mysql_fetch_assoc($result))
{
    $o = new stdClass;
    $o->pw = $row['password'];
    $o->mail = $row['mail'];
    array_push($arr, $o);
}

You don't really need to use push much in php, you can use the empty brackets to tack it on. Not sure if it makes a difference but I find the brackets easier. Also, O doesn't seem to be defined in this code, or reset in the loop. That is probably where the problem comes from, although i'm not very clear about your question overall. Good Luck

$sql="select password, mail from account";
$result=mysql_query($sql);
$arr=array();
while($row=mysql_fetch_assoc($result))
{
    //define/reset o here
    $o->pw=$row['password'];
    $o->mail=$row['mail'];
    $arr[] = $o;
}
echo json_encode($arr);

I think you need to instance a new object for each iteration of your loop. Right now there's only one $o being written to for each iteration of the loop, which is why they all appear to have the same value: they ARE the same.

Try this:

while($row=mysql_fetch_assoc($result))
{
    $o = new stdClass();
    $o->pw=$row['password'];
    $o->mail=$row['mail'];
    array_push($arr, $o);
}