Imagick::getCompression

The ImageMagick PHP function for getCompression returns an integer representing the value associated with the ImageMagick Compression constant. You'll get numbers from 0 to 13, each representing a different particular type of compression. If printed out, the ImageMagick constants for compression come out as...
imagick::COMPRESSION_UNDEFINED 0
imagick::COMPRESSION_NO 1
imagick::COMPRESSION_BZIP 2
imagick::COMPRESSION_DXT1 3
imagick::COMPRESSION_DXT3 4
imagick::COMPRESSION_DXT5 5
imagick::COMPRESSION_FAX 6
imagick::COMPRESSION_GROUP4 7
imagick::COMPRESSION_JPEG 8
imagick::COMPRESSION_JPEG2000 9
imagick::COMPRESSION_LOSSLESSJPEG 10
imagick::COMPRESSION_LZW 11
imagick::COMPRESSION_RLE 12
imagick::COMPRESSION_ZIP 13
Every time I have used this, whether on a jpeg image, a png image, a gif image, or a bmp image, it has always returned '0' as a value. There's a good chance that this is simply a value that is set by means of get/set, as opposed to actually producing values for a given image.
Some sample code :
<?php
 // Author: holdoffhunger@gmail.com
 
 // Imagick Type
 // ---------------------------------------------
 $imagick_type = new Imagick();
 
 // Open File
 // ---------------------------------------------
 
 $file_to_grab = "image_workshop_directory/test.bmp";
 
 $file_handle_for_viewing_image_file = fopen($file_to_grab, 'a+');
 
 // Grab File
 // ---------------------------------------------
 $imagick_type->readImageFile($file_handle_for_viewing_image_file);
 
 // Get Quantum Range
 // ---------------------------------------------
 
 $imagick_type_compression = $imagick_type->getCompression();
 
 // Print Results
 // ---------------------------------------------
 print("<pre>");
 print($imagick_type_compression);
 print("</pre>");
?>