<?php
    echo "<label>Please select the Competition:&nbsp;&nbsp;<select name='opt'>";
    while ($row = mysqli_fetch_array($result)) {
    echo "<option value='" . $row['comp_id'] ."'>" . $row['compname'] ."</option>";
    }
    echo "</select></label>";
    print_r($row['comp_id']);
    ?>

<input type="text" name="comp_id" placeholder=" (the value from the selected item ">