How can I convert the case of the characters in a string to lower case/upper case randomly in PHP?

How can I convert the case of the characters in a string to lower case/upper case randomly?, Example:

$str = "alternating case";

And I want to get a result like this:

$newstr = "aLtErNaTiNg cAsE";

and

$newstr = "AlTeRnAtInG CaSe";

Is this possible? Thanks