function not run!

hi

i edited single.php in theme directory, i pu this code

<?php 

$tank = ($_GET['lang']); 

if ($tank=="fa") {
     $myImage = "<IMG SRC =assets/img/scenert.png>";
} 

if ($tank=="en") {
     $myImage = "<IMG SRC =assets/img/scenerten.png>";
}
?> 

<?php
/**
 * @package WordPress
 * @subpackage Default_Theme
 */

get_header(); ?>

<div id="maincontainer">
<div id="contentwrapper">
<div id="contentcolumn" class="background:#999999 url() right no-repeat;
">
<div class="innertube">test<?php print $myImage; ?></div>
</div>
</div>

<div id="rightcolumn">
<div class="innertube"> 

	<?php if (have_posts()) : ?>

		<?php while (have_posts()) : the_post(); ?>

			<div <?php post_class() ?> id="post-<?php the_ID(); ?>">
				<div class="entry">
					<?php the_content('Read the rest of this entry &raquo;'); ?>
				</div>

			</div>

		<?php endwhile; ?>

		<div class="navigation">
			<div class="alignleft"><?php next_posts_link('&laquo; Older Entries') ?></div>
			<div class="alignright"><?php previous_posts_link('Newer Entries &raquo;') ?></div>
		</div>

	<?php else : ?>

		<h2 class="center">Not Found</h2>
		<p class="center">Sorry, but you are looking for something that isn't here.</p>
		<?php get_search_form(); ?>

	<?php endif; ?>

 </div>
</div>
</div>

	</div>

in this line

<div class="innertube">test<?php print $myImage; ?></div>

<?php print $myImage; ?> not run in my page
what’s wrong??

i tested myself code in a single page

<?php 

$tank = ($_GET['lang']); 

if ($tank=="fa") {
     $myImage = "<IMG SRC =assets/img/scenert.png>";
} 

if ($tank=="en") {
     $myImage = "<IMG SRC =assets/img/scenerten.png>";
}
?>
<div class="innertube">test<?php print $myImage; ?></div>

and works fine