gistfile1.aw

<?php

$someVar = 'some value';
add_action('admin_init', function() {
  # I want access to $someVar in here, and don't want it to be a global.
  # Is there a way to pass $someVar into the callback as a local variable?
});

$someVar = 'some value';
add_action('admin_init', function() use($someVar) {
$something = $someVar;
});

Okay - use did it. Thanks @rcky! The other two options didn't work for me.

$someVar = 'some value';
add_action('admin_init', function() use($someVar) {
    echo $someVar;
});

Just a note here. This syntax will only work in php 5.3+

Yep.