Create variable $pathinfo and $random to get block 15 random lines of html file

I am working on a php website and would like to echo 15 random line from a html file. So far I just got 15 lines but the problem is I get the code from the html file and not 15 block lines from the text. How could I define 2 variables $pathinfo and $random to write my code in a way that gets me the correct solution?

My code:

     <?php  

    $selected_file = $_POST['radio1'];
    // get the filename of the file
    $fileinfo = pathinfo($selected_file);
    $filename = $fileinfo['dirname'] . DIRECTORY_SEPARATOR . $fileinfo['filename'];
    $password = 'code';




if (isset($_POST['submitradio']))
{ 
     echo '<div class="imageselected">';
     echo '<img src="'.$selected_file.'" /></br>'.PHP_EOL;
     echo '</div>';
    // check to see if a html file named the same also exists
    if(file_exists("$filename.html"))
    {

        echo "<form action='test_result.php' method='post'>";
        echo '<div class="Password">';
        echo 'Type in password to view full Script';

        echo "<label><div class=\"Input\"><input type='password' name='passIT' value='passit'/></div>";
        echo "<input type='submit' name='submitPasswordIT' value='Submit Password'/></div>";
        echo '</div>';
        echo '</form>';
        echo "$filename.html shares the same name as $selected_file";



        $lines =  file("$filename.html");

        for($x = 1;$x<=15;$x++) {

        echo $lines [rand(0, count($lines)-1)]."<br>";
        }
        // end of forloop

        }
        // end of check
          // start Sorrytext

            else
            {
             echo '<div class="NoScript">';

                echo "We apologize. No Script available for this movie.";
                echo '</div>';
            }

         // end Sorrytext
}
// End of submitradio
if($_POST['submitPasswordIT']){
if ($_POST['passIT']== $password ){
echo "You entered correct password";
$dirs = glob("*", GLOB_ONLYDIR);
$pathinfo = ($dirs.'/'.$lines.'/html');
include($pathinfo);
}
else{
echo "You entered wrong password";
}
}

?>

Help would be very much appreciated:)