This code displays a form that the user can use to resize an image on upload. When the form is submitted the image is uploaded to a tempory location where it is then resized and saved into the directory set in the code.

Note: If allowing user uploads the data submitted MUST be checked to stop people uploading code that can compramise the server.

<?php
// If the form has been submitted do this
if ( $Submit ) {  

// Temporary upload image name
$original_image = $_FILES['filename']['tmp_name'];

// Get the image dimensions
$size=GetImageSize( $original_image );

// Name to save the image as - in this case the same as the original
$new_image = $_FILES['filename']['name'];

// Maximum image width
$max_width = "200";

// Maximum image height
$max_height = "90";

// Resize the image and save
exec("convert -size {$size[0]}x{$size[1]} $original_image -thumbnail $max_widthx$max_height $new_image");

echo "File uploaded<br>";

echo "<img src=\"".$new_image."\">";
}
else { ?>
<p>File to upload:</p>
<form method="post" action="<?php echo $PHP_SELF; ?>" enctype="multipart/form-data"> 
<input type="file" name="filename"  />
<input type="Submit" name="Submit" value="Submit" />
</form>
<?php } ?>