#include 
#include 
#include 
 
#include 
 
int main() {
   std::string str = "-3.14asd.asd.a0.23.asdfj234d.123.34++23.0";
   boost::regex rgx("\\-?\\d+\\.\\d+");
   std::copy(
      boost::sregex_token_iterator(str.begin(), str.end(), rgx),
      boost::sregex_token_iterator(),
      std::ostream_iterator (std::cout, " ")
   );
   getchar();
}

if (!preg_match("/^[a-zA-Z0-9-\s]{3,24}$/", $_REQUEST[user_name])) {
    $errormsg .= "Use only letters and numbers";
}

function IsEmail(email) {
    var regex = /^([a-zA-Z0-9_\.\-\+])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
    return regex.test(email);
}

if (!preg_match('/^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,6})$/', $_REQUEST[user_email])) {
    $errmsg .= "Please enter a valid email address
";
}