// Do not confuse with { instead of [. It's okey.
// $export_data and $data both are same (Input array).
{
"0": {
    "customer_id": 1,
    "name": "John Stevens",
    "Date of 1 Purchase": "2014-08-05T00:00:00+0000",
    "Date of 2 Purchase": "2014-09-05T00:00:00+0000",
    "Date of 3 Purchase": "2014-10-05T00:00:00+0000",
    ...
    ...
    ... 350 Cols ...
    }
"1": {
    ...
    }
...
...
"999 Rows"
}

$r = 1;
$filename = FILE_PATH . 'galliyan.xlsx';

$header = array_keys($export_data[0]);

$objPHPExcel = new PHPExcel();
$col = 0;
foreach ($header as $field) {
    $objPHPExcel->getActiveSheet()->setCellValueByColumnAndRow($col, 1, $field);
    $col++;
}
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
$objWriter->save($filename);
chmod($filename, 0777);
$r++;

$objPHPExcel = PHPExcel_IOFactory::load($filename);
foreach($export_data as $row) {
    $col = 0;
    foreach ($row as $ro) {
        $objPHPExcel->getActiveSheet()->setCellvalueByColumnAndRow($col, $r, $ro);
        $col++;
    }

    $r++;
}
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
$objWriter->save($filename);
chmod($filename, 0777);

foreach ($data as $row) {
    if (!$flag) {
        $header = array();
        // display field/column names as first row
        $header = array_keys($row);
        $header = $this->setExcelHeaders($header);
        $this->createExcelFile($dir_name, $filename, $header, $export_type);
        $flag = TRUE;
    }

    array_walk($row, array($this, 'cleanData'));
    array_push($values, $row);

}

$values = $this->setValues($values);
$this->writeExcelFile($dir_name, $filename, $values);

function setExcelHeaders($hdrs) {
    $header = '';
    foreach ($hdrs as $title_val) {
        $header .= $title_val . "t";
    }
    return $header;
}

function createExcelFile($dir_name, $filename, $header, $export_type = '') {
    $fp = fopen($dir_name . "/" . $filename, 'w');
    fwrite($fp, "$headern");
    fclose($fp);

    $permission = Configure::read('Config.PERMISSION');
    if ($export_type == "") {
        chmod($dir_name, $permission);
    }
    chmod($dir_name . "/" . $filename, $permission);
}

public function cleanData(&$str) {
    $str = preg_replace("/t/", "\t", $str);
    $str = preg_replace("/r?n/", "\n", $str);
    if (strstr($str, '"'))
        $str = '"' . str_replace('"', '""', $str) . '"';
}

private function setValues($all_vals) {
    $data = '';
    for ($i = 0; $i < count($all_vals); $i++) {
        $line = '';
        foreach ($all_vals[$i] as $value) {
            if ((!isset($value)) || ( $value == "")) {
                $value = "t";
            }
            else {
                $value = str_replace('"', '""', $value);
                $value = '"' . $value . '"' . "t";
            }
            $line .= $value;
        }
        $data .= trim($line) . "n";
    }
    return $values = str_replace("r", "", $data);
}

function writeExcelFile($dir_name, $filename, $data) {
    $fp = fopen($dir_name . "/" . $filename, 'a');
    fwrite($fp, "$data");
    fclose($fp);
}