Record in the corded session of a Link and destroy another session to do site translation

How Can I make that by clicking on a flag it records in a session the data referring to your language

• Brazil = = > saves the string " br "
• United States = = > saves the string " usa "

And clicking on one destroy the other

Estou indo por esse principio mais não sei se é o correto
lng = $_REQUEST['lng'];
$_SESSION['lng'] = $lng; 


<a href="<?echo $nome_do_arquivo?>?lng=br"><img src="img/br.jpg" width="28" 
height="16" alt="Image" data-retina="true"/></a>

<a href="<?echo $nome_do_arquivo?>?lng=usa"><img src="img/lang_en.png" 
width="28" height="16" alt="Image" data-retina="true"/></a>

<a href="<?echo $nome_do_arquivo?>?lng=fran"><img src="img/lang_fr.png"  
width="28" height="16" alt="Image" data-retina="true"/></a>

<a href="<?echo $nome_do_arquivo?>?lng=spain"><img src="img/lang_es.png" 
width="28" height="16" alt="Image" data-retina="true"/></a>