espero que te sea de utilidad
saludos
<?php
$shtml="<table>";
$shtml=$shtml."<tr>";
$shtml=$shtml."<td>Pelos</td><td>suma</td><td>Totales</td>";
$shtml=$shtml."</tr>";
$shtml=$shtml."<tr>";
$shtml=$shtml."<td>1</td><td>C4325</td><td>2000.00</td>";
$shtml=$shtml."</tr>";
$shtml=$shtml."<tr>";
$shtml=$shtml."<td>2</td><td>DX456</td><td>1000.00</td>";
$shtml=$shtml."</tr>";
$shtml=$shtml."<tr>";
$shtml=$shtml."<td>3</td><td> </td><td>-1000.00</td>";
$shtml=$shtml."</tr>";
$shtml=$shtml."<tr>";
$shtml=$shtml."<td>4</td><td>A18-TG</td><td>1000.00</td>";
$shtml=$shtml."</tr>";
$shtml=$shtml."<tr>";
$shtml=$shtml."<td></td><td>suma</td><td>=SUM(c2:c5)</td>";
$shtml=$shtml."</tr>";
$shtml=$shtml."</table>";
$scarpeta=""; //carpeta donde guardar el archivo.
//debe tener permisos 775 por lo menos
$sfile=$scarpeta."Pelos.xls"; //ruta del archivo a generar
$fp=fopen($sfile,"w");
fwrite($fp,$shtml);
fclose($fp);
echo "<a href='".$sfile."'>Haz click aqui</a>";
?>