hidden form

[eluser]shahnawazahmed[/eluser]
hello developers

i want assign a randomly generated code to the database field hidden form . i generate code with $activation = md5(uniqid(rand(), true)); and now i want to assign to the activation field in the db , so i am using this code in the form

echo form_hidden('activation', '$activation');

but its not assigning the andom code to the field .