Here is simple Excel file generation function, very fast and exactly .xls file.
$filename = "sample_php_excel.xls";
$data = array(
array("User Name" => "Abid Ali", "Q1" => "$32055", "Q2" => "$31067", "Q3" => 32045, "Q4" => 39043),
array("User Name" => "Sajid Ali", "Q1" => "$25080", "Q2" => "$20677", "Q3" => 32025, "Q4" => 34010),
array("User Name" => "Wajid Ali", "Q1" => "$93067", "Q2" => "$98075", "Q3" => 95404, "Q4" => 102055),
);
to_xls($data, $filename);
function to_xls($data, $filename){
$fp = fopen($filename, "w+");
$str = pack(str_repeat("s", 6), 0x809, 0x8, 0x0, 0x10, 0x0, 0x0); // s | v
fwrite($fp, $str);
if (is_array($data) && !empty($data)){
    $row = 0;
    foreach (array_values($data) as $_data){
        if (is_array($_data) && !empty($_data)){
            if ($row == 0){
                foreach (array_keys($_data) as $col => $val){
                    _xlsWriteCell($row, $col, $val, $fp);
                }
                $row++;
            }
            foreach (array_values($_data) as $col => $val){
                _xlsWriteCell($row, $col, $val, $fp);
            }
            $row++;
        }
    }
}
$str = pack(str_repeat("s", 2), 0x0A, 0x00);
fwrite($fp, $str);
fclose($fp);
}
function _xlsWriteCell($row, $col, $val, $fp){
if (is_float($val) || is_int($val)){
    $str  = pack(str_repeat("s", 5), 0x203, 14, $row, $col, 0x0);
    $str .= pack("d", $val);
} else {
    $l    = strlen($val);
    $str  = pack(str_repeat("s", 6), 0x204, 8 + $l, $row, $col, 0x0, $l);
    $str .= $val;
}
fwrite($fp, $str);
}