PHP Validation to require One of Two Form Fields filled in - php

Question

I am developing a site that uses javascript to handle many functions and PHP based Captcha code to validate the form field.
It works great, but the form will submit if none of the fields are filled in.
I need one of two form fields ['email' or 'phone'] filled in, but neither can be left blank.
The error message can be the same error message thrown up when the captcha field is left blank or filled in incorrectly.
I am new to PHP code and cannot figure out for the life of me how to call the function.
The function code is:
<?php
if(isset($_POST['send'])){
$emailFrom = "clientemail.com";
$emailTo = "clientemail.com";
$subject = "Contact Form Submission";
$first_name = strip_tags($_POST['first_name']);
$last_name = strip_tags($_POST['last_name']);
$email = strip_tags($_POST['email']);
$phone = strip_tags($_POST['phone']);
$message = strip_tags(stripslashes($_POST['message']));
$body .= "First Name: ".$first_name."\n";
$body .= "Last Name: ".$last_name."\n";
$body .= "Email: ".$email."\n";
$body .= "Phone: ".$phone."\n";
$body .= "Comments: ".$message."\n";
$headers = "From: ".$emailFrom."\n";
$headers .= "Reply-To:".$email."\n";
if($_SESSION['security_code'] == $_POST['security_code']){
$success = mail($emailTo, $subject, $body, $headers);
if ($success){
echo '<p class="yay">Your e–mail has been sent.</p>';
}
} else {
echo '<p class="oops">Something went wrong. Hit the back button and try again.</p>';
}
} else {
?>
The form field:
<form action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']); ?>" method="post" id="contact" name="contact">
<fieldset>
<label for="name"><span style="color:#bf252b;">*</span>First Name</label>
<input type="text" id="first_name" name="first_name" minlength="2"/>
<label for="name">Last Name</label>
<input type="text" id="last_name" name="last_name" minlength="2"/>
<label for="email"><span style="color:#bf252b;">*</span> Email</label>
<input type="text" id="email" name="email" />
<label for="phone"><span style="color:#bf252b;">*</span> Phone</label>
<input type="text" id="phone" name="phone" />
<label for="message">Message</label><div style="clear:both;"></div>
<textarea id="message" name="message" cols="40" rows="10" ></textarea>
<img src="../captcha.php" id="captcha" alt="captcha" style="padding:25px 0px 20px 0px;" />
<label for="security_code">Enter captcha</label>
<input type="text" id="security_code" name="security_code" autocomplete="off" class="required"/>
<button type="submit" id="send" name="send" style="margin:0px 0px 10px 12px;">Send!</button>
</fieldset>
</form>
<?php } ?>
There is a .php document for running captcha, but am I right in thinking there is a simple solution for this; some extra code in the existing code that will fix my issue? I really want to avoid javascript and plugins if I can help it.
Thanks in advance!!

Answer 1

Try this,
if($_SESSION['security_code'] == $_POST['security_code'] && (!empty($email) || !empty($phone))) {
instead of
if ($_SESSION['security_code'] == $_POST['security_code']) {
This is not convenient way to validate form but I hope this will help.

Answer 2

Add the required attribute to the fields you need required.

Answer 3

Fix your code!
Notice: Undefined variable: body in /../sendform.php on line 14
Do that:
$body = "First Name: ".$first_name."\n";
$body .= "Last Name: ".$last_name."\n";
$body .= "Email: ".$email."\n";
$body .= "Phone: ".$phone."\n";
$body .= "Comments: ".$message."\n";
Solution
if(($_SESSION['security_code'] == $_POST['security_code']) AND
(!empty($email) OR !empty($phone)) ) {
In other words:
Security code must be match
Email or Phone can not be empty