Digest::MD5.hexdigest 'test str1&test str2&test str3&test str4'

Digest::MD5.hexdigest 'test str1test str2test str3test str4'

php -r 'echo md5("test str1&test str2&test str3&test str4");'

ad0efdf609e99ec50d9333dc0bd1c11a

function sendHttpRequest(w){
    var url = "http://www.md5.cz/getmd5.php";
    var idWhat = document.getElementById('what');
    var params = "what=" + idWhat.value;
                           ^^^^ Pardon???