Generating alphanumeric gibberish?

What's a simple (preferably loopless) way to generate a large amount of alphanumeric gibberish? Any language is acceptable.

In PHP, I thought this would be perfect:

hexdec(mt_rand(1.e999999999, 1.e9999999999));

But it doesn't work due to restrictions on the length of int. :(

>>2
I want it on one line.

Also:

rtrim(base64_encode(mcrypt_create_iv(13000, MCRYPT_DEV_URANDOM)), '=');