PHP PEAR - Problems with files with over 200 row

good morning,

i have a problem with php pear, which generates excel sheets. this is my php code:

<?PHP
include_once "/Writer.php";

    $xls =& new Spreadsheet_Excel_Writer();
    $xls -> setVersion(8); 


    $format_titel =& $xls->addFormat();
    $format_titel->setBold();
    $format_titel->setAlign('left');
    $format_titel->setSize('14');
    $format_titel->setFgColor('grey');
    $format_titel->setBorder(2);
    $sheet =& $xls->addWorksheet("Tab_1");


    for ($A=0; $A<=59; $A++) {
        $Zeile++;
        $s=0;   

        for ($B=0; $B<=1; $B++){
            $Text_Daten_Excel =  $Daten_Excel[$A][$B]; //$s++;
            $sheet -> write(($A+3), ($B), "TEST TEXT", $format_titel);
        }
    }

    $xls -> send("Sheet.xlsx");  
    $xls->close();
    $xls->sendFile();  
?>

This code works fine. A Excel sheet will generate.

But if I change the line number to more than 59

for ($A=0; $A<=59; $A++) {

the excel sheet will generate but i cant open it. I get this message:

The file is damaged and can not be opened.