Trying to Load Compiled Extension

Hello, fellow developers:

Information, documentation and tutorials about creating PHP extensions 
online is rather scarce, but I was able to pull together a few tutorials 
and build an extension. You can download and view the source code from 
http://www.dnscrawler.com/rawsockets.tar.gz. I compile it as follows:

phpize
./configure --with-rawsockets
make
make install

for RedHat EL 5 and

phpize
./configure --with-rawsockets --with-php-config=/usr/bin/php-config
make
make install

for Mac OS X Snow Leopard 10.6.2. It compiles without error and says 
that the extension has been copied to the proper directory. However, if 
I try to load the extension either with dl('rawsockets.so') or 
extension=rawsockets.so in the INI file, I get the error "PHP Warning:  
PHP Startup: Invalid library (maybe not a PHP library) 'rawsockets.so'  
in Unknown on line 0 phpinfo()". If, per some suggestions I found 
online, I try to load it with 
zend_extension=/usr/lib/php5/extensions/rawsockets.so, I get the error 
"/usr/lib/php5/extensions/rawsockets.so doesn't appear to be a valid 
Zend extension."

I'm going to back off a bit on this and start with a simple "Hello, 
World" extension (I know, I probably should have done that first), but 
while I do that, I would really appreciate some input as to why this 
compiles without any errors OR warnings but doesn't load with a cryptic, 
unhelpful error message.

I did run `strace php -i` and got the following output related to my 
extension:

open("/usr/lib/php5/extensions/rawsockets.so", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0 
\3\0\0004\0\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=7757, ...}) = 0
mmap2(NULL, 8212, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) 
= 0xb7b6c000
fadvise64(3, 0, 8212, POSIX_FADV_WILLNEED) = 0
mmap2(0xb7b6d000, 8192, PROT_READ|PROT_WRITE, 
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0) = 0xb7b6d000
close(3)                                = 0
mprotect(0xb7b6d000, 4096, PROT_READ)   = 0
munmap(0xb7b6c000, 8212)                = 0
write(2, "PHP Warning:  PHP Startup: Inval"..., 107PHP Warning:  PHP 
Startup: Invalid library (maybe not a PHP library) 'rawsockets.so'  in 
Unknown on line 0
) = 107

Thanks for your help in advance,

Nick