Form Email/URL

PHP provides two alternatives for validating the form data items which are strings but are expected to be a representation of Email ID or a URL. One way to check the form element contains email/URL is with the use of RegEx (regular expressions), and the other, more convenient approach is to use filter_var() function. Let us apply both these methods and validate email and URL submitted by a form to a PHP script.

The HTML Form used for this chapter is as follows −

Open Compiler

<h1>Email and URL Validation</h1><form action="hello.php" method="POST"><p><label for="email">Enter your email:</label><input type="text" id="email" name="email"></p><p><label for="URL">Enter your website<label><input type = "text" id="URL" name="url"></p><input type="submit"></form>

Validation with Regex

PHP’s built-in function library includes the preg_match() function that performs a regular expression match.

preg_match(string$pattern,string$subject,array&$matches=null,int$flags=0,int$offset=0):int|false

This function searches subject for a match to the regular expression given in pattern. preg_match() returns 1 if the pattern matches given subject, 0 if it does not, or false on failure.

A valid email ID should satisfy the following regular expression −

"/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix"

Similarly, a valid URL should satisfy the following regular expression −

"/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i"

The following function returns “1” or “0” if the string is a valid email ID.

functioncheckemail($str){return(!preg_match("/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix",$str))?FALSE:TRUE;}

Example

Let us use the checkmail() function to check whether the email field in the above HTML is valid or not, with the help of following PHP code −

<?php         
   function checkemail($str) {
      return (!preg_match("/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@
         ([a-z0-9\-]+\.)+[a-z]{2,6}$/ix", $str)) ? FALSE : TRUE;
   }
   if ($_SERVER["REQUEST_METHOD"] == "POST") {
      $email = $_POST['email'];
      if(!checkemail($email)){
         echo "Invalid email address.";
      } else {
         echo "Valid email address.";
      }
   }
?>

The HTML form is rendered as below −

Test the PHP code by entering valid/invalid email string in the email field.

The following checkURL() function checks if a string represents a valid or invalid URL, and returns “1 or “0”.

functioncheckURL($str){return(!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)
      [-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$str))?FALSE:TRUE;}

Example

The URL field extracted from the $_POST array is given as argument to the above function.

<?php         
   function checkURL($str) {
      return (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]
         *[-a-z0-9+&@#\/%=~_|]/i", $str)) ? FALSE : TRUE;
   }
   if ($_SERVER["REQUEST_METHOD"] == "POST") {
      $url = $_POST['url'];
      if(!checkURL($url)){
         echo "Invalid URL.";
      } else {
         echo "Valid URL.";
      }
   }
?>

You can test the above code by entering URL string in the URL field of the above form.

Using filter_var() function

The built-in filter_var() function filters a variable with a specified filter.

filter_var(mixed$value,int$filter=FILTER_DEFAULT,array|int$options=0):mixed

Depending on the enumerated filter ID as the value of $filter parameter, the $value parameter is checked and the function returns the filtered data, or false if the filter fails.

There are various predefined filter ID constants available −

Sr.No	ID & Description
1	FILTER_VALIDATE_BOOLReturns true for “1”, “true”, “on” and “yes”. Returns false otherwise.
2	FILTER_VALIDATE_DOMAINValidates whether the domain name label lengths are valid.
3	FILTER_VALIDATE_EMAILValidates whether the value is a valid e-mail address.
4	FILTER_VALIDATE_IPValidates value as IP address
5	FILTER_VALIDATE_URLValidates value as URL

Example

The following PHP script validates the email and URL data submitted by the HTML for above −

<?php
   if ($_SERVER["REQUEST_METHOD"] == "POST") {
      $email = $_POST['email'];
      $url = $_POST['url'];

      if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
         echo "Invalid email format and please re-enter valid email\n"; 
      }
      else
      echo "Email entered is in valid format\n";

      if (!filter_var($url, FILTER_VALIDATE_URL)) {
         echo "Invalid URL format and please re-enter valid URL\n"; 
      }
      else
      echo "URL entered is in valid format\n";
   }
?>

You can test the performance of the above script by entering valid/invalid email/URL.