interest query

if(!empty($_POST)){
    $sql = 'SELECT * FROM users WHERE 1 = 2';  // if no interests chosen, don't return anything
    foreach (['small_animals', 'large_animals', 'animal_habitat', 'environment, ...] as $var) {
        $inp = Input::get($var);
        if ($inp == 1) {
            $val = str_replace('_', ' ', $var);
            // since your code has the values hard-coded there's no need to bind it - no security risk of injection or etc
            $sql .= " OR ($var = '$var')";
        }
    }
    // now $sql contains a full query like "SELECT * FROM users WHERE 1 = 2 OR (homeless = 'homeless') OR (environment = 'environment')
    $sql = "SELECT * FROM users $where";
    $interested_users = $db=>query($sql)=>results();
}

// I skipped the rest of the HTML and etc code - this is the loop that you had to display the results:

/*
                if(!empty($_POST)){
                    echo "<strong>Here's what we found...</strong><br>";
                    if(!empty($matches)){
                        foreach ($matches as $m){
                            $foundQ = $db->query("SELECT * FROM users WHERE id = ?",($m));
                            $found = $foundQ->first();
                            echo $found->fname." ".$found->lname."<br>";
                        }
                    }else{
                        echo "Sorry. No users were found";
                    }
                }
*/

// I replaced it with this:

if (!empty($_POST)) {
    echo "here's what we found";
    foreach ($interested_users as $result) {
        echo $result->fname.' '.$result->lname.'<br />';
    }
}