if(preg_match('/(?i)msie/', $_SERVER['HTTP_USER_AGENT'])) {
if(preg_match('/(?i)Trident/5/', $_SERVER['HTTP_USER_AGENT'])) {
    echo "IE9";
}
elseif(preg_match('/(?i)Trident/4/', $_SERVER['HTTP_USER_AGENT'])) {
    echo "IE8";
}
elseif(!preg_match('/(?i)Trident/4/', $_SERVER['HTTP_USER_AGENT']) AND preg_match('/(?i)msie 7/', $_SERVER['HTTP_USER_AGENT'])) {
    echo "IE7";
}
elseif(preg_match('/(?i)msie [1-6]/', $_SERVER['HTTP_USER_AGENT'])) {
    echo "IE1 à IE6";
}}