I ran through a tutorial for updating to PHP 5.2 via RPMs';
http://wiki.centos.org/HowTos/PHP_5.1_To_5.2

In the tutorial I did;

wget http://yum.cocoiti.com/CentOS/5/RPMS/i686/php-mcrypt-5.2.10-1.i686.rpm

rpm -i --nodeps php-mcrypt-5.2.10-1.i686.rpm
warning: php-mcrypt-5.2.10-1.i686.rpm: Header V3 DSA signature: NOKEY, key ID 9f63b763

Restarted apache, mcrypt wasn't installed. (I used a phpinfo() page.)

However.. it installed mcrypt.so to;
/usr/lib/php/modules/

But all the other .so files are stored in;
/usr/lib64/php/modules/

I copied the file to the lib64 directory, and restarted apache. Still didn't work.

So.. then.. I tried to unstall, by doing this;

rpm -qa |grep php-m

Returned;

php-mysql-5.2.10-1.el5.centos
php-mcrypt-5.2.10-1
php-mbstring-5.2.10-1.el5.centos

Then I typed in;

rpm -e php-mycrypt-5.2.10-1
error: package php-mycrypt-5.2.10-1 is not installed

Yeah.. so now I'm stuck, don't know how to make php use it.. I also found a file;
/etc/php.d/mcrypt.ini
Contents:
; Enable mcrypt extension module
extension=mcrypt.so

Am I totally screwed or what?

Sounds like you downloaded the 32bit mcrypt module on a 64 bit php installation, find the 64 bit module and install that.

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Ok, I thought i686 was 64 bit, but on more inspection I see that I agree with you that I need x86_64.

That doesn't resolve the issue with how to remove the invalid i686 rpm.

oops sorry

rpm -e php-mycrypt-5.2.10-1
error: package php-mycrypt-5.2.10-1 is not installed

You typoed, you put mycrypt.

_________________
Paid support
How to ask for help
1. Give details of your problem
2. Post any errors
3. Post relevant logs.
4. Don't hide details i.e. your domain, it just makes things harder
5. Be polite or you'll be eaten by a grue

Very bizzare, today I tried to install php-mycrypt, and I got this error;

Transaction Check Error:
  package php-mcrypt-5.2.10-1.i686 (which is newer than php-mcrypt-5.2.9-2.el5.centos.3.x86_64) is already installed

So then! I did;

rpm -e php-mcrypt-5.2.10-1.i686

And it worked! lol

So I guess, if you are running CentOS 64 bit, the correct lettering includes the type of rpm, in this case i686, in order to uninstall. I hope this helps someone out there with similar issues with installing the wrong type of rpm on their linux box..