I was just looking for the same thing and I realized that, once again, my thinking is different because I am old school. I go all the way back to BASIC and PERL and sometimes I forget how easy things really are in PHP.
I just made this function to take all settings from the database where their are 3 columns. setkey, item (key) & value (value) and place them into an array called settings using the same key/value without using push just like above.
Pretty easy & simple really
// Get All Settings
$settings=getGlobalSettings();
// Apply User Theme Choice
$theme_choice = $settings['theme'];
.. etc etc etc ....
function getGlobalSettings(){
    $dbc = mysqli_connect(wds_db_host, wds_db_user, wds_db_pass) or die("MySQL Error: " . mysqli_error());
    mysqli_select_db($dbc, wds_db_name) or die("MySQL Error: " . mysqli_error());
    $MySQL = "SELECT * FROM systemSettings";
    $result = mysqli_query($dbc, $MySQL);
    while($row = mysqli_fetch_array($result)) 
        {
        $settings[$row['item']] = $row['value'];   // NO NEED FOR PUSH
        }
    mysqli_close($dbc);
return $settings;
}
So like the other posts explain... In php there is no need to "PUSH" an array when you are using 
Key => Value
AND... There is no need to define the array first either. 
$array=array();
Don't need to define or push. Just assign $array[$key] = $value; It is automatically a push and a declaration at the same time.
I must add that for security reasons, (P)oor (H)elpless (P)rotection, I means Programming for Dummies, I mean PHP.... hehehe I suggest that you only use this concept for what I intended. Any other method could be a security risk. There, made my disclaimer!