PHP Math SUM af en MySQL return

PHP kode 

 $number = $number + ($firstnumber+$secondbumer);

PHP kode 

 $number += ($firstnumber+$secondbumer);

Kode 

$number = 0;
$query = mysql_query("SELECT * FROM tal where") or die(mysql_error());
while($row = mysql_fetch_array( $query )) {
    $firstnumber = $row['firstnumber'];
    $secondnumber = $row['secondnumber'];
    $number += ($firstnumber+$secondnumber);
}

Kode 

$number = array();
$query = mysql_query("SELECT * FROM tal where") or die(mysql_error());
while($row = mysql_fetch_array( $query )) {
    $firstnumber = $row['firstnumber'];
    $secondnumber = $row['secondnumber'];
    $number[] = ($firstnumber+$secondnumber);
}

$number = array_sum($number);