Setting a globally used function to run automatically

[eluser]hightower[/eluser]
So is it a done thing to have this in my header_view.php file:

Code:

$var = $some_custom_function();

echo $var['test'];
echo $var['test2'];

Because that would seemingly be the answer to my question, but I didn't know whether it was considered bad coding practice to run the function from my helper within a view file?