- preg_replace: documentation ( source)
<?php
echo preg_replace(
'#\[country ln=(.*?)\] | \[cn=(.*?)\](.*?)\[/cn\] | \[/country\] | ,\s*#xie',
"(('$1')?'$1:<br />':'').(('$2')?'<img src=\"$2.png\" border=\"0\" alt=\"$3\" class=\"ui-icon-country\" />$3':'')",
'[country ln=COUNTRIES][cn=us]USA[/cn], [cn=hu]Hungary[/cn], [cn=ru]Russia[/cn], [cn=gb]Great Britain[/cn][/country]'
);