The sybase_fetch_array and sybase_fetch_object functions seem to cast float values to integers from the second resultset and onwards.
The following script doesn't echo two floats, but a float and an integer(1.23 and 4). 

<?php
/*
Test table layout and data:
create table test (id  float)
go
insert into test values(1.23)
insert into test values(4.56)
go
*/
$conn = sybase_pconnect("foo", "bar", "baz");
$q = sybase_query("SELECT id FROM test");
while($res = sybase_fetch_array($q)) {
    echo "$res[0]<br>";
}
?>

My configure line is:
./configure --with-sybase-ct=/opt/sybase --enable-ftp --with-apache=../apache_1.3.27 --with-gd --enable-trans-sid --disable-debug --enable-bcmath --with-zlib --without-mysql