php random characters generator [duplicate]

This question already has an answer here:

• using chr + rand to generate a random character (A-Z) 4 answers

in php we have rand() method to generate random numbers

    eg: $rand_num = rand(1, 9);

output : generates random number between 1 to 9.

In the same way I want to generate random characters between 'a' to 'z'. Any ideas.