Server Side Form Validation using Regular Expressions

form.php

<?php

//Declaring the variables
$error_name = '';
$error_email= '';
$error_gender ='';

//Validation part
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
	$name = $_POST['name']; 
	$email = $_POST['email']; 
	$gender = $_POST['gender']; 
	
	//only characters and space is allowed
	if(!preg_match('/^[a-z ]+$/i', $name)) {
		$error_name = "Alowed charaters are a-z ";
	}
	
	$regex = '/^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$/';
	if(!preg_match($regex, $email)) {
		$error_email = "Invalid email";
	}
	
	if(empty($gender)) {
		$error_gender = "Select gender";
	}
	
	if(empty($error_name) && (empty($error_email) && empty($error_gender))) {
		//your insert to database
	}
	

}
?>

<form method="post">
  <?php print $error_name?>
  <br>
  <label>Name</label>
  <input type="text" name="name" value="">
  <br><br>
  <?php print $error_email?>
  <br>
  <label>Email</label>
  <input type="email" name="email" value="">
  <br><br>
  <?php print $error_gender?>
  <br>
  <label>Gender</label>
  <select name="gender">
    <option value="male">Male</option>
    <option value="female">Female</option>
  </select>
  <br><br>
  
  <input type="submit" name="submit" value="Submit">
</form>