Con questo script in PHP possiamo caricare le immagini sul nostro server attraverso questo form.

$uploadpath: è la cartella dove saranno caricate le nostre immagini
$max_size: la massima dimmensione dei file jpg che possiamo caricare, possiamo configurarlo a nostro piacimento.
$allowtype: le estensioni concesse per caricare.

Codice PHP:
<?php

$uploadpath 
'upload/';      // directory to store the uploaded files
$max_size 2000;          // maximum file size, in KiloBytes
$alwidth 900;            // maximum allowed width, in pixels
$alheight 800;           // maximum allowed height, in pixels
$allowtype = array('bmp''gif''jpg''jpe''png');        // allowed extensions

if(isset($_FILES['fileup']) && strlen($_FILES['fileup']['name']) > 1) {
  
$uploadpath $uploadpath basename$_FILES['fileup']['name']);       // gets the file name
  
$sepext explode('.'strtolower($_FILES['fileup']['name']));
  
$type end($sepext);       // gets extension
  
list($width$height) = getimagesize($_FILES['fileup']['tmp_name']);     // gets image width and height
  
$err '';         // to store the errors

  // Checks if the file has allowed type, size, width and height (for images)
  
if(!in_array($type$allowtype)) $err .= 'The file: <b>'$_FILES['fileup']['name']. '</b> not has the allowed extension type.';
  if(
$_FILES['fileup']['size'] > $max_size*1000$err .= '<br/>Maximum file size must be: '$max_size' KB.';
  if(isset(
$width) && isset($height) && ($width >= $alwidth || $height >= $alheight)) $err .= '<br/>The maximum Width x Height must be: '$alwidth' x '$alheight;

  
// If no errors, upload the image, else, output the errors
  
if($err == '') {
    if(
move_uploaded_file($_FILES['fileup']['tmp_name'], $uploadpath)) { 
      echo 
'File: <b>'basename$_FILES['fileup']['name']). '</b> successfully uploaded:';
      echo 
'<br/>File type: <b>'$_FILES['fileup']['type'] .'</b>';
      echo 
'<br />Size: <b>'number_format($_FILES['fileup']['size']/10243'.''') .'</b> KB';
      if(isset(
$width) && isset($height)) echo '<br/>Image Width x Height: '$width' x '$height;
      echo 
'<br/><br/>Image address: <b>http://'.$_SERVER['HTTP_HOST'].rtrim(dirname($_SERVER['REQUEST_URI']), '\\/').'/'.$uploadpath.'</b>';
    }
    else echo 
'<b>Unable to upload the file.</b>';
  }
  else echo 
$err;
}
?> 
<div style="margin:1em auto; width:333px; text-align:center;">
 <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="POST" enctype="multipart/form-data"> 
  Upload File: <input type="file" name="fileup" /><br/>
  <input type="submit" name='submit' value="Upload" /> 
 </form>
</div>