In file sapi/apache/mod_php4.c, function sapi_apache_ub_write() check return code of fwrite,
and set connection_status accordingly
But in sapi/cgi/cgi_main.c, the equivalent function
sapi_cgibin_ub_write() does not check the return
code. Indeed, in the cgi version I dont
see where connection_status is set to PHP_CONNECTION_ABORTED.
As a result, I have a script that never end, although
IgnoreUserAbort is set to Off, and connection_status()
still returns 0 though client is dead.

Changing in cgi_main.c .._ub_write() to :

static int sapi_cgibin_ub_write(const char *str, uint str_length)
{
        int ret;
        ret=fwrite(str, 1, str_length, stdout);
        if (ret != str_length) {
                PG(connection_status) = PHP_CONNECTION_ABORTED;
                if (!PG(ignore_user_abort)) {
                        zend_bailout();
                }
        }
        return ret;
}

does not solve my problem, because error (and ignored SIGPIPE) occurs in fflush(), not in fwrite()
so I had to change sapi_cgibin_flush() too.

static void sapi_cgibin_flush(void *server_context)
{
        if (fflush(stdout) <0) {
                PG(connection_status) = PHP_CONNECTION_ABORTED;
                if (!PG(ignore_user_abort)) {
                        zend_bailout();
                }
        }
}

hope this helps