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.
Basic Form Structure
The HTML Form used for this chapter is as follows −
<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",$str))?FALSE:TRUE;}
Example: Check the Email Field
Let us use the checkmail() function to check whether the email field in the above HTML is valid or not, with the help of following PHP code −
<?php
function checkemail($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;}</pre>
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 $value parameter is checked and the function returns the filtered data, or false if the filter fails.
Predefined Filter ID Constants
There are various predefined filter ID constants available −
Sr.No ID & Description 1 FILTER_VALIDATE_BOOLReturns true for "1", "true", "on" and "yes". Returns false otherwise. 2 FILTER_VALIDATE_DOMAINValidates whether the domain name label lengths are valid. 3 FILTER_VALIDATE_EMAILValidates whether the value is a valid e-mail address. 4 FILTER_VALIDATE_IPValidates value as IP address 5 FILTER_VALIDATE_URLValidates value as URL
Example
The following PHP script validates the email and URL data submitted by the HTML for above −
<?php
if ($_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.
