<form method="post" action="send_email.php">
  <label for="name">Name:</label>
  <input type="text" id="name" name="name" required>

  <label for="email">Email:</label>
  <input type="email" id="email" name="email" required>

  <label for="message">Message:</label>
  <textarea id="message" name="message" required></textarea>

  <button type="submit">Send</button>
</form>

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
  // Retrieve form input
  $name = test_input($_POST["name"]);
  $email = test_input($_POST["email"]);
  $message = test_input($_POST["message"]);

  // Validate form input
  if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    echo "Invalid email format";
    exit;
  }

  // Compose email message
  $to = "youremail@example.com";
  $subject = "New form submission";
  $body = "Name: $name\nEmail: $email\nMessage:\n$message";

  // Send email
  if (mail($to, $subject, $body)) {
    echo "Email sent successfully";
  } else {
    echo "Email sending failed";
  }
}

function test_input($data) {
  $data = trim($data);
  $data = stripslashes($data);
  $data = htmlspecialchars($data);
  return $data;
}
?>