Signal Uncaught

Hi all.

I tried to write some scirpts in php, and met a problem while using lighttpd with mod_fastcgi. Here's the code below:
---------------------------------------------------
<?php
declare(ticks = 1);

function sig_handler($signo)
{
             echo "Caught signal...\n";
}

echo "Installing signal handler...\n";

pcntl_signal(SIGUSR1, "sig_handler", FALSE);

echo"Generating signal SIGTERM to self...\n";

echo posix_getpid();
posix_kill(posix_getpid(), SIGUSR1);

echo "Done\n"

?>
---------------------------------------------------
The issue is, the signal could only be caught for the first time, and then always failed until lighttpd was restarted. If I switched mod_fastcgi to mod_cgi in lighttpd.conf, the signal could be caught everytime without problem. I'm using lighttpd 1.4.20 & php 5.2.6 with default configuration.

Thanks in advance.