Convert Facebook uid into Facebook username!

<?php
$lines=array();
$fp=fopen('file.txt', 'r');
while (!feof($fp))
{
    $line=fgets($fp);
    $line=trim($line);
    $lines[]=$line;

 
}
fclose($fp);
 
$n = 0;
while ($n < count($lines)){
    $response = file_get_contents('http: slash slash graph dot facebook dot com/'.$lines[$n]);
    $array = json_decode($response, true);
 
    
 
    $file = 'address.txt';
    // Open the file to get existing content
    $current = file_get_contents($file);
    // Append a new person to the file
    if (empty($array['username'])) {
       $current .= $array['id']." AT facebook dot com"."\r\n";;
    }
    else {
       $current .= $array['username']." AT facebook dot com"."\r\n";
    }
    
    // Write the contents back to the file
    file_put_contents($file, $current);
    $n = $n + 1;
    }
?>