User $variables through-out plugin with out using globals.

I do apologize if my question is a big confusing.
Im building a plugin that takes data and displays it in a loop. Then I would take the ID number and get results from another table.
eg

global $wpdb, $bp;
$fname =  'mike';
$lname= 'freemond';
$entries = $wpdb->get_results("SELECT * FROM table WHERE column1 = $fname AND column2 = $lname ORDER BY id");
if( $entries ) {
  foreach( $entries as $entry ) {
        $contentid = $entry->id,
	$firstname = $entry->content1,
	$lastname = $entry->content2,
	$city = $entry->content3,
);

echo $contentid;
echo $firstname;
echo $lastname;
echo $city;
$phonenumber = $wpdb->results("SELECT * FROM contact WHERE person = $contentid");
echo $phonenumber;
... ect...
}
}

(This is just an example code..)

so the above loop will display id,first name, last name, city, and phonenumber.
What I would like to do is have a function for the phone numbers
eg.

function phonenumber(){
global $wpdb;
$phonenumber = $wpdb->results("SELECT * FROM contact WHERE person = $contentid");
echo $phonenumber;
}

Then use it in my loop.

global $wpdb, $bp;
$fname =  'mike';
$lname= 'freemond';
$entries = $wpdb->get_results("SELECT * FROM table WHERE column1 = $fname AND column2 = $lname ORDER BY id");
if( $entries ) {
  foreach( $entries as $entry ) {
        $contentid = $entry->id,
	$firstname = $entry->content1,
	$lastname = $entry->content2,
	$city = $entry->content3,
);

echo $contentid;
echo $firstname;
echo $lastname;
echo phonenumber(); <-- here.
... ect...
}
}

I looked into add_filter/apply_filters. But I couldn’t find a simple break down of an example. I was able to do the following.

function a($one){
$one = '1';
return $one;
}add_filter('addthis', 'a');

function b(){
$one = apply_filters('addthis', 'a');
$two = '2';
$three = $two + $one;
echo $three
};

$three would echo 3.
But it didn’t work as planned when I put it all together.
Once again, I do apologize if my question is a bit confusing.
Many thanks -Mike.