Program received signal SIGSEGV, Segmentation fault.
0x400c08d8 in chunk_free (ar_ptr=0x40115420, p=0x818fe68) at malloc.c:2942
malloc.c:2942: No such file or directory.
(gdb) bt
#0  0x400c08d8 in chunk_free (ar_ptr=0x40115420, p=0x818fe68) at malloc.c:2942
#1  0x400bffea in malloc_extend_top (ar_ptr=0x40115420, nb=56) at malloc.c:2464
#2  0x400c0635 in chunk_alloc (ar_ptr=0x40115420, nb=56) at malloc.c:2793
#3  0x400c00c5 in __libc_malloc (bytes=45) at malloc.c:2561
#4  0x805f169 in _emalloc (size=29) at alloc.c:115
#5  0x80782f4 in php3_sybase_get_column_content (sybase_ptr=0x80ca250, offset=21, 
    result=0x818fab8, column_type=111) at functions/sybase.c:664
#6  0x80785e9 in php3_sybase_query (ht=0x80c5a20, return_value=0x80a46f8, list=0x80b5bd0, 
    plist=0x80b5ba4) at functions/sybase.c:770
#7  0x804fd68 in phpparse () at control_structures_inline.h:930
#8  0x8058d50 in php3_parse (yyin=0x80c0a58) at main.c:1534
#9  0x80594cd in main (argc=2, argv=0xbffffda4) at main.c:1842

This is using the FreeTDS dblib implementation - however, it appears that the failure is in a call to emalloc(); of course, this should be rock solid code. So my next guess is a data segment corruption of some sort; and we all know how much fun that can be to track down....

Here's the script:
$conn = sybase_connect("mysqlserver", "user", "password");
if ($conn) {
    if (sybase_select_db("mydatabase", $conn)) {
        $sql = "SELECT * FROM mytable";
        $result = sybase_query($sql, $conn);
        if ($result) {
            $nrows = sybase_num_rows($result);
            for ($i = 0; $i < $nrows; $i++) {
                $value = sybase_result($result, $i, "somefield");
                echo "$value<BR>\n";
            }
            sybase_free_result($result);
        }
    }
    sybase_close($conn);
} else {
    echo "No connection\n";
}

I'm using the FreeTDS static libs as the shared ones didn't do anything... (still figuring that one out).