Learn PHP required form fields validation with examples

After ensuring that fields are not empty, the next step is to verify that the data submitted is in the correct format. PHP provides powerful tools like filter_var() and Regular Expressions (RegEx) for this purpose.

1. Validating E-mail

The easiest and safest way to check if an e-mail address is well-formed is to use the filter_var() function with the FILTER_VALIDATE_EMAIL filter.

<?php
  $email = test_input($_POST["email"]);
  if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    $emailErr = "Invalid email format";
  }
?>

2. Validating URL

To validate a website URL, we use a Regular Expression. The pattern below checks if the URL syntax is valid and allows for protocols like http, https, and ftp.

<?php
  $website = test_input($_POST["website"]);
  if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i", $website)) {
    $websiteErr = "Invalid URL";
  }
?>

3. Validating Name (Letters Only)

For a name field, you usually want to restrict input to only letters and white spaces. We use the preg_match() function to enforce this rule.

<?php
  $name = test_input($_POST["name"]);
  if (!preg_match("/^[a-zA-Z-' ]*$/", $name)) {
    $nameErr = "Only letters and white space allowed";
  }
?>

4. Why Validation Matters

Note: While filter_var() is great for emails, complex strings like URLs often require Regular Expressions to handle different protocols and domain extensions correctly.

PHP Form URL/E-mail Validation

1. Validating E-mail

2. Validating URL

3. Validating Name (Letters Only)

4. Why Validation Matters