PHP Form Validation

July 19, 2022 Santosh PHP Basics No Comments

PHP Form Validation

– There are 2 ways to validate forms. The first is using Javascript, which is also known as client-side validations and the second one is using PHP, which is also known as server-side validations. In this tutorial, we’ll cover server-side validations by using PHP functions.

Common PHP Form Validations

1. Empty String: The following code snippet will check that the input field is not left blank while submitting the form. If the user leaves any required field empty, in this example Name, this code will generate an error message. This is the most common PHP form validation.

if (empty ($_POST["name"])){
$errorMessage = "Name field can not be left blank. Please enter your name.";
echo $errorMessage;
} else{
$name = $_POST["name"];
}

2. Validate String: The following code snippet checks if the input field contains only alphabets and whitespace. So, if the Name input field does not get the valid input from the user, then the below code will generate an error message as shown below:

$name = $_POST ["name"];

if (!preg_match ("/^[a-zA-z]*$/", $name) ){
$errorMessage = "Only Alphabets and Whitespaces are allowed in Name field.";
echo $errorMessage;
} else{
echo $name;
}

3. Validate Number: The following code snippet validates that the field will only contain a numeric value. If the mobile number doesn’t receive numeric data from the user, as input then the following code will generate an error message as shown below:

$mobilenumber = $_POST ["mobile_number"];

if (!preg_match ("/^[0-9]*$/", $mobilenumber) ){
$errorMessage = "Only numeric value is allowed in Mobile number field.";
echo $errorMessage;
} else{
echo $mobilenumber;
}

4. Validate Email: The valid email must contain @ &. symbols. PHP provides various methods to validate email input fields. We can use regular expressions to validate the email address as shown below:

$email = $_POST ["email_address"];
$email_valid_pattern = "^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$^";

if (!preg_match ($email_valid_pattern, $email) ){
$errorMessage = "Entered email address is invalid.";
echo $errorMessage;
} else{
echo "Your valid email address is: " .$email;
}

We can even use the inbuilt feature of PHP to validate emails: FILTER_VALIDATE_EMAIL as below:

$email = $_POST ["email_address"];
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
$errorMessage = "Entered email address is invalid.";
echo $errorMessage;
} else{
echo "Your valid email address is: " .$email;
}

Both of these methods are popularly used in PHP form validation, you can use any of these.

5. Input Field Length Validation: The following code snippet validates that the mobile field will have exactly 10 digits. If the entered mobile number value comprises less or more than 10 digits then the following code will generate an error message as shown below:

$mobilenumber = strlen ($_POST ["mobile_number"]);
$length = strlen ($mobilenumber);

if ( $length < 10 && $length > 10){
$errorMessage = "Mobile must have 10 digits.";
echo $errorMessage;
} else{
echo "Your Mobile number is: " .$mobilenumber;
}

6. Validate URL: The following code snippet validates that the website URL is valid. If the URL is not valid, it will generate an error message as shown below:

$website_url = $_POST["website"];
$url_valid_pattern = "/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i";
if (!preg_match($url_valid_pattern,$website_url)){
$errorMessage = "Entered website URL is invalid.";
echo $errorMessage;
} else {
echo "Entered website URL is: " .$websiteURL;
}

7. Button Click Validate: The following code snippet validates that the user clicks on the submit button and sends the form data to the server using one of the following methods – GET or POST.

if (isset ($_POST['submit']) {
echo "Submit button is clicked.";
if ($_SERVER["REQUEST_METHOD"] == "POST"){
echo "Data is sent using POST method ";
}
} else {
echo "Data is not submitted via form.";
}

Below is the complete code with a form and all the above mentioned