<?php
  /*** a non rfc compliant URL ***/
  $url = "index.php";

  /*** try to validate the URL ***/
  if(filter_var($url, FILTER_VALIDATE_URL, FILTER_FLAG_SCHEME_REQUIRED) === FALSE)
  {
    /*** if there is no match ***/
    echo "Sorry, $url is not valid!";
  }
  else
  {
    /*** if the URL is valid ***/
    echo "The URL, $url is valid!";
  }
?>

<?php
  $email = "someone@exa mple.com";

  if(!filter_var($email, FILTER_VALIDATE_EMAIL))
  {
    echo "E-mail is not valid";
  }
  else
  {
    echo "E-mail is valid";
  }
?>

<?php
  $email = "someone@exa mple.com";

  if(!filter_var($email, FILTER_VALIDATE_EMAIL))
  {
    echo "E-mail is not valid";
  }
  else
  {
    echo "E-mail is valid";
  }
?>