PHPExcel需要很长时间来加载xls，与xlsx一样好

Question

Good day. I have xls file that looks like this:

+----+-------+--------+
| ID | PRICE | STATUS |
+----+-------+--------+
|  1 |  1000 |      1 |
|  2 |  1000 |      3 |
|  4 |  1324 |      5 |
|  8 |  3141 |      1 |
+----+-------+--------+

As you can see there is not too much rows and cols. But when i try to save it like XLS file and then load to PHPExcel like this:

$objPHPExcel = PHPExcel_IOFactory::load('1.xls');

It takes eternity to load, and Server CPU and RAM usage grows like magic tree. But when i try to do the same stuff with XLSX it works like LeBron James. Like this:

$objPHPExcel = PHPExcel_IOFactory::load('1.xlsx');

PHP extensions: zip, xml, gd, xmlreader, xmlwriter, xmlrpc are installed and works. PHP ver 5.6.12 FastCGI.