Thanks, guys! Highly appreciate your responses.
ScottMSanders' method works, but still need to set time larger because the spreadsheet is too large.
1. Do you guys know how to go through sheet from column 'A' to 'AM'? Below program doen't work well, it just returns column 'A'.
$str .= $objPHPExcel->getActiveSheet()->getCell("$k$j")->getValue()." ";
2. Another problem with my work is to read large number. The large number like 1000203000000 is showed in spreadsheet in scientific data like 1.000203E+12, so it is read as 1.000203E+12 through phpexcel, while I want the original data like 1000203000000.
I try to use "$objPHPExcel->getActiveSheet()->getStyle("$k$j")->getNumberFormat()->setFormatCode('0'); ", but it doesn't work.
Your guys have any idea about the large number?