New Post: How to properly write values with leading zeroes with its unknown length

I've created custom value binder, match them, and write using

$cell->setValueExplicit($value, PHPExcel_Cell_DataType::TYPE_STRING);

But still recieve notifications in Excel about numbers written as text. I'd apply some custom number format for it (e.g. ###### or something), but values can contain spaces in different places, and the numbers length is not known(its range approximately 8-15)....