I am here again with a strange question.

First, I’m using ACF plugin for adding cistom fields. My code looks somethink like that:

global $testMe;
$testMe = 0;
function my_acf_update_value( $value, $post_id, $field ) {
    global $testMe;
    $testMe = $value;
    return $value;
}
add_filter('acf/update_value/key=field_5308e5e79784b', 'my_acf_update_value', 10, 3);
echo $testMe; // -> print 0, not the $value!?

The problem is that I want, after the filter apply, $testMe to contain the value of $value.

Any ideas where I’m wrong?