for a school project, makes a remote server take a shot with a webcam, copies it to the local server and transfers it to the client

image.php

<?php
  // Overwrites the local copy of an image after at least TIME_DELTA seconds
  // Images are first captures by camera (HEAD request to other website)
  // and then copied here from the other server.
  // Next they are transfered to the user as an image, so you can treat this PHP-File as an image.
  // 
  // By Jan Schnitker, 2015, published under the UNLICENSE, read about it here: http://unlicense.org/

  // send the right headers
  header("Content-Type: image/jpg"); // transmit as jpg
  //header("Content-Length: " . filesize($localImage)); (could be done later, but not necessary)
  
  $TIME_DELTA = 5; // get new image after at least 5 seconds
  
  $imgNos = [188,189];
  $imgNo = $imgNos[0]; // default value: first image
  
  // if given by GET, extract the image id the user wants to get (...php?i=X), X is the ID
  // then we take the X-th element from the array $imgNos, and thats our image number :)
  if ( isset($_GET["i"]) ) {
    $i = intval($_GET["i"]); // this is the number given by GET, eq: ....php?i=5 would make i=5
    if( $i>=0 and $i<count($imgNos) ) { // not exceeding the array
      $imgNo = $imgNos[$i]; // set imgNo to the corresponding image number
    }
  }
  
  // construct filenames/urls
  $urlUpdate = "http://it-projekt-muenster.de/images/ip-cam".$imgNo.".php";
  $urlImage = "http://it-projekt-muenster.de/images/".$imgNo."/webcam.jpg";
  $localImage = "./".$imgNo.".jpg";
  
  // if the file-time is greater or equal to 5seconds, we will request a new picture from the webcam and download it
  if( time() - filemtime ( $localImage ) >= $TIME_DELTA ) {
    // send request to update the image on serverside
    $ch = curl_init(); // create curl connection
    curl_setopt($ch, CURLOPT_URL, $urlUpdate); // set url
    curl_setopt($ch, CURLOPT_NOBODY, true); // dont wanna have the body
    curl_setopt($ch, CURLOPT_HTTPHEADER, []);  // set: header only
    $resultHead = curl_exec($ch); // execute request (connect, send, receive)
    curl_close($ch); // close connection
    
    // download new image from webcam
    $resultCopy = file_put_contents( $localImage, file_get_contents( $urlImage ));
  } 
  
  // either way, open the file and stream it as an image to the user
  // open the file in a binary mode
  $fp = fopen($localImage, 'rb');
  
  // dump the picture and stop the script
  fpassthru($fp); 
  exit;
?>