Problem downloading data to Excel using PHP "pack" function - php

Question

I have a PHP application that downloads MySQL table data to a spreadsheet on the client machine. I found some code in numerous places on the web that works fine for Open Office Scalc on a machine running Redhat. The problem I ran into was when I tried to download to an MS Excel on a Windows PC rather than to an Open Office spreadsheet. The problem seems to be associated with the length of the string inserted into a cell. If it is too long, Excel thinks the file is corrupt and won't load it. "Too long" seems to be about 255 characters, even though the MS Excel specs say 32,000 is the maximum length.
To investigate the problem further, I tried downloading the same data as a tab-separated values file and let Excel convert it to a spreadsheet. Using that method, there was no problem loading very long strings into the spreadsheet cells. So strings much longer than 255 characters can in fact be inserted into Excel cells, but just not with the code I am using, even though that code works with Open Office. Using tsv files would not solve our problem, because the long strings have carriage returns that we want to retain, and carriage returns are interpreted as row separators when a tsv file is loaded into a spreadsheet.
The PHP function that writes a string to a spreadsheet cell is:
function xlsWriteLabel($Row, $Col, $Value ) {
$L = strlen($Value);
echo pack("ssssss", 0x204, 8 + $L, $Row, $Col, 0x0, $L);
echo $Value;
return;
}
The other necessary code for transfers to spreadsheets in addition to the above function can be found at:
http://www.appservnetwork.com/modules.php?name=News&file=article&sid=8
I haven't found any explanations as to the meanings of the various arguments passed to the "pack" function in the above code, and I'm wondering if changing one the arguments in the function above could solve the problem.
So, if anyone has a solution to this problem, I'd be interested in hearing it.

Answer 1

...unless your text has double quotes.
What you should use is proper delimiters from the ASCII char set.
Seq Dec Hex Acro Name
^\ 28 1C FS File Separator
^] 29 1D GS Group separator
^^ 30 1E RS Record Separator
^_ 31 1F US Unit separator
I don't know php but in perl a print statement might look like:
print chr(30), "Field1", chr(30), "Field2", chr(30), "Field3", chr(31);

Answer 2

I have written a simple approach to generate absolute excel file.
A simple function.
First you convert your contents to an Array (it is very simple and everybody know.). Then pass the array to my function given below.
<?php
//array to excel
function arrayToExcel($array, $filename='List')
{
if (!is_array($array) or !is_array($array[0])) return false;
$xl = pack("ssssss", 0x809, 0x8, 0x0, 0x10, 0x0, 0x0); //begining of excel file
$i = 0;
foreach ($array as $key => $val)
{
$j=0;
foreach ($val as $cell_key => $cell_val)
{
$cell_val = trim($cell_val);
$length = strlen($cell_val);
//checking cell value is a number and the length not equal to zero
if(preg_match('/^[0-9]*(\.[0-9]+)?$/', $cell_val) && $length!=0) {
$xl .= pack("sssss", 0x203, 14, $i, $j, 0x0); //writing number column
$xl .= pack("d", $cell_val);
}
else {
$xl .= pack("ssssss", 0x204, 8 + $length, $i, $j, 0x0, $length); //writing string column
$xl .= $cell_val;
}
$j++;
} //end of 2nd foreach
$i++;
} //end of first foreach
$xl .= pack("ss", 0x0A, 0x00); //end of excel file
$filename = $filename.".xls";
header("Pragma: public");
header('Content-Type: application/vnd.ms-excel');
header("Content-Disposition: attachment; filename=$filename");
header("Cache-Control: no-cache");
echo $xl;
} //end of arrayToExcel function
//eg: arrayToExcel($myarray, "contact_list");
?>

Answer 3

Surround your cell values with double quotes "", it will allow you to import the data in a tsv or csv format without having to worry about the carriage returns being interpreted as a new row. You could also use the fputcsv function from PHP to export a tsv or csv file that excel can read.
This is the slightly more efficient version of their functions thank you linked too, but I don't know if the format they output is actually correct for excel or not.
function xlsBOF(){
echo pack("s6", 0x809, 0x8, 0x0, 0x10, 0x0, 0x0);
}
function xlsEOF(){
echo pack("ss", 0x0A, 0x00);
}
function xlsWriteNumber($Row, $Col, $Value){
echo pack("s5d", 0x203, 14, $Row, $Col, 0x0, $Value);
}
function xlsWriteLabel($Row, $Col, $Value){
$L = strlen($Value);
echo pack("s6A*", 0x204, 8 + $L, $Row, $Col, 0x0, $L, $Value);
}