php Email form / if / else if / error messages - php

Question

I have tried to create php email form. The form was basically working, but I wanted to add validation functions like I did on 'name'
However, It doesn't work when I empty 'name' and just sent an email.
Any help would be really appreciated.
htmlfile
<form action="php_mini.php" method="post">
Name:
<input type="text" name="name">
<span class="error">* <?php echo $nameErr;?></span>
<br><br>
Email:
<input type="text" name="email">
<span class="error">* <?php echo $nameErr;?></span>
<br><br>
Phone:
<input type="text" name ="phone">
<br><br>
Comment:
<!--<textarea name="comment"></textarea>-->
<!--<input type = "text" name = "comment">-->
<textarea name="comment" rows="5" cols="40"></textarea>
<span class="error">* <?php echo $nameErr;?></span>
<br><br>
<input type="submit" value="Submit">
</form>
php
echo '<pre>';
print_r( $_POST );
echo '</pre>';
$headers = 'MIME-Version: 1.0' . "\r\n" .
'Content-type: text/html; charset=iso-8859-1' . "\r\n" .
'From: Design_customers <customers.com' . " \r\n" .
//'Reply-To: vader#deathstar.com' . "\r\n" .
'X-Mailer: PHP/' . phpversion();
//error msg
$nameErr = $emailErr = $phoneErr = "";
$name = $email = $comment = $phone = "";
//receiver
if (empty($_POST["name"])) {
$nameErr = "Name is required";
} else {
$name = test_input($_POST["name"]);
}
$email = $_POST['email'];
/*$message = $_POST['comment'];*/
$message = 'You got a message from a customer.:
Name: '.$_POST['name'].'
Email: '.$_POST['email'].'
Phone: '.$_POST['phone'].'
Comment: '.$_POST['comment'];
//sender
$from = 'From: Customer';
$subject = 'Customer Inquiry';
mail( $email, $subject, $message, $from );

Answer 1

use if(isset($_POST["name"])) to stop the error. [Notice: Undefined index: name in C........]
better you have validate this form with java Script. i have attached a snipped part of you form with javascript.
<form action="" method="post" onsubmit="return(Validate());" name="myform">
Name:
<input type="text" name="name">
<span class="error">* <div id="name_error" style="color:red;"></div> </span>
<br><br>
</form>
<script type="text/javascript">
<!--
// Form validation code will come here.
function Validate()
{
if( document.myform.name.value == "" )
{
alert( "Please provide your name!" );
name_error.textContent = "Name is Required.!";
document.myform.name.focus() ;
return false;
}
return( true );
}
//-->
</script>