Description:
------------
While comparing crc32()'s output with other languages' 
CRC32 functions I note that sometimes the result is 
different. Unfortunately all other engines, such as Perl 
Digest::Crc32, String::CRC32, Archive::Zip, give always  
the same value.

I wasn't able to understand which format leds to this 
misbehaving, and I also tried to run crc32() of failing 
strings' MD5 hashes: the result is different.

Reproduce code:
---------------
#This works:
php -r "echo crc32('htmlhptaccuin');"
121189226
perl -MString::CRC32 -e 'print crc32("htmlhptaccuin")'
121189226

#This doesn't:
php -r "echo crc32('html:hp_taccuino');"
-1565398511
perl -MString::CRC32 -e 'print crc32("html:hp_taccuino")'
2729568785

Expected result:
----------------
I expect to have the same CRC32 hash everywhere, so I 
expect to get 2729568785 in the above example.