<?
    $db = dbmopen('req.db', "n");
    $in = "1234567890";
    dbminsert($db, "ID", $in);
    $out = dbmfetch($db, "ID");
    dbmclose($db);
    echo "in  -$in-\n";
    echo "out -$out-\n";
?>

am using the distribution "Win32 Binaries packaged as zip" from
http://www.php3.org/downloads.php
filename : php-4.0.3pl1-Win32.zip

save code as say db.php3
run in dos window to exclude interference from webserver

d:\tmp>\php\php.exe db.php3
X-Powered-By: PHP/4.0.3pl1
Content-type: text/html

in  -1234567890-
out -234567890-

As you can see the first char is dropped. For anything up to 9 chars everythings OK. More than 9, first char is dropped. Tried using all alhpa strings, same behaviour. 
Looked at req.db flat file database, everything looks ok there. 

2<nl>
ID10<nl>
1234567890