my array

gistfile1.txt

Array
(
    [0] => Array
        (
            [myid] => 31
            [fname] => Dwayne
            [mi] => 
            [lname] => Alexander
            [degrees] => PHD
        )

    [1] => Array
        (
            [myid] => 28
            [fname] => Sam
            [mi] => 
            [lname] => Beene
            [degrees] => 
        )

    [2] => Array
        (
            [myid] => 13
            [fname] => Richard
            [mi] => E
            [lname] => Gil
            [degrees] => BA
        )

    [3] => Array
        (
            [myid] => 25
            [fname] => Carlo
            [mi] => 
            [lname] => Gonzalex
            [degrees] => 
        )

    [4] => Array
        (
            [myid] => 23
            [fname] => Subi
            [mi] => 
            [lname] => Shakya
            [degrees] => 
        )

)


need to group by last name so it displays like this:

A
 - all last names that start with A

B
 - all last names that start with B

etc.