php how to check a string for more than 5 consonants in a row

Question

As a spam filter I want to block any comments that contain

djgalkgjlkdg

or any other excessive amount of consonants in a row.

I thought of maybe having an array of consonants and then check the comment with it, but seems too long and cumbersome.

Do you know of any way I can do this without guzzling memory?

Answer 1

if(preg_match("~[bcdfghjklmnpqrstvwxyz]{4,}~", $string)......

Answer 2

preg_match('/[bcdfghjklmnpqrstvwxz]{6}/i', $input) perhaps?