Solution may be following (as for me, this variant rather implies questions than gives answers).

If you apply following method
$workbook->setVersion(8);
You will be able to record long strings by means of $worksheet->writeString()

But after that coding problems appeared which I haven’t solved yet. By attempt to recode or set up $worksheet-->setInputEncoding() the picture that is typical for me now is “file has been damaged so seriously that its reconstruction is impossible”.

I would be very thankful if someone has any ideas concerning the thread.

The problem is similar to the one described here
http://pear.php.net/bugs/bug.php?id=1805.

But the variants of its solution don’t work…

Generally speaking, this problem is partially solved.
First you are to link up php_iconv.dll library in the unit Extensions of php.ini file. Generally it was enough for me but I’ve found one more way just in case:

1. $workbook->setVersion(8);

2. $worksheet->setInputEncoding('CP1251');

3. In Spreadsheet/Excel/writer.php after the line 67 (method send())
we write
header("Content-Encoding: windows-1251");

4. Spreadsheet/Excel/writer/Workbook.php:200 correct
$this->_codepage = 1200 // FIXME: should change for BIFF8

5. Spreadsheet/Excel/writer/Workbook.php:1445 correct
$encoding = 1; // assume there are no Unicode strings

But! File size now can be no more than < ~8224kb
Maybe someone has got something better?