This is a basic contact form to build off of.

con_form.php

<?php //Let's Contact Form This Thing UP!

// Start Your PHP Sessions 
  session_start();

// Set the contact page variable for redirection later
	$contact_page = get_permalink(48);

// Create the necessary variable that will be used in detecting errors
	$errorFound = false;
	$errorReport = "";

// Create variables and retrieve the values for each element of the main form. Sanitize the data.
// Includes a ternary fallback for placeholder.js in IE 8, since the placeholder text goes through as the value when empty.
	$firstName = ($_POST['firstName']=='First Name *')?'':stripslashes(trim($_POST['firstName']));
	$lastName = ($_POST['lastName']=='Last Name *')?'':stripslashes(trim($_POST['lastName']));
	$phone = ($_POST['userPhone']=='Phone Number *')?'':stripslashes(trim($_POST['userPhone']));
	$email = ($_POST['userEmail']=='Email Address')?'':stripslashes(trim($_POST['userEmail']));
	$comment = stripslashes(trim($_POST['userComments']));
		
// check for spam in a hidden field
	$human_test = stripslashes(trim($_POST['human_test']));
	
// validateForm()
// This function verifies that the form has been filled out correctly
	function validateForm() {
		
// Start by making the necessary variables "global" so that they can be accessed outside of this function
		global $errorFound, $errorReport, $errorField, $firstName, $lastName, $phone, $email;

// Check to make sure that the necessary form elements were filled out
		$errorField = array();
		if(empty($firstName)) {
			$errorFound = true;
			$errorReport .= "<p class=\"subtitle\">Please provide your first name.</p>\n";
			$errorField['firstName'] = true;
		}
		if(empty($lastName)) {
			$errorFound = true;
			$errorReport .= "<p class=\"subtitle\">Please provide your last name.</p>\n";
			$errorField['lastName'] = true;
		}
		if(empty($phone)){
			$errorFound = true;
			$errorReport .= "<p class=\"subtitle\">Please provide your phone number.</p>";
			$errorField['phone'] = true;
		}
		
// If any errors were found, then return false
		if($errorFound) {
			return false;
		}
// If no errors were found, then return true
		return true;
	}
	
// validContent()
// This function filters through the content of the form and checks for possible spam issues
	function validContent() {

// Start by making the necessary variables "global" so that they can be accessed outside of this function
		global $firstName, $lastName, $phone, $email, $comment, $human_test;
		$spamFound = false;

// Set up the default spam values to check against
		$spamValues = array('http:', 'href=', 'SEO');

// set up the list of user input values to check for spam
		$checkVars = array($firstName, $lastName, $phone, $email, $comment);

// Loop through each input value and check it against each spam value
		foreach($checkVars as $var){
			foreach($spamValues as $sv){
// If there is a match, change spamFound to true				
				if(strstr($var, $sv)!=false){$spamFound = true;}
			}
		}
		
// Check to see if the human test field was filled out		
		if(!empty($human_test)) { $spamFound = true; }

// If any problems were found, then return false
		if($spamFound) {
			return false;
		}
// Otherwise, return true
		return true;
	}

// Check to see if the form has been submitted
	if(isset($_POST['submit'])) {

// If it has been submitted, begin validating the form
// Create variables necessary for sending the form information and fill the body of the email with the appropriate information.
		$toAddress = "";
		$bccToAddress = "";

		if(validateForm() == false) {
// If the form does not pass validation, then do nothing for right now.  This will be handled later on in the script.
		}
		else {
			
// Create the body of the email
			$body = "\nThe information provided in this email was submitted from example.com.\n"; // Change the domain name on this line
			$body .= "Please contact the individual below within 24 hours of receiving this message.\n\n\n";
			$body .= "NAME:  " . $firstName . " " . $lastName . "\n";
			$body .= "PHONE:  " . $phone . "\n";
			$body .= "EMAIL:  " . $email . "\n";
			$body .= "\nCOMMENTS:\n" . $comment . "\n";
			$body .= "\n\n\n";
			$body .= "-- End of Message.";
			
// Finalize the details of the email before sending it.
// If the form's content passes the spam filters, then send the form as you normally would
			if(validContent()) {
				$toAddress = "[email protected]"; // Change the toAddress to reflect the recipient of the email
				$bccToAddress = "[email protected]"; // Change the bccToAddress to reflect any backup email addresses. If there aren't any bcc addresses, comment out this line and the bcc declaration in the header.
				$fromAddress = "[email protected]"; // Change the from address to reflect the email domain of the website
				$emailSubject = "Contact Form from - example.com - " . $subject_date; // Update the domain for the email header
				$emailHeader = "From: " . $fromAddress . "\r\n";
				$emailHeader .= "Reply-To: " . $fromAddress . "\r\n";
//				$emailHeader .= "Bcc: " . $bccToAddress . "\r\n"; // Comment this out if you are not utilizing the BCC address field
				$emailHeader .= "X-Mailer: PHP/" . phpversion(); 

// Finaly, email the results of the form to the appropriate person.  Allow the script to continue to run at this point.
				mail($toAddress, $emailSubject, $body, $emailHeader);

// Redirect the user to the thank you page if everything worked properly			
				header('Location: '.$contact_page.'?thank_you=true');
			} else {
// if an issue occured, redirect the user to an error page
				header('Location: '.$contact_page.'?error_code=1');
			}
		}
	}
?>
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title></title>
</head>
<body>
<?php
	if($_GET['thank_you'] == 'true'){
		echo "<div class='successBox'>\n";
		echo "<p>Your form has been submitted successfully.</p>\n";
		echo "<p class='subtitle'>We will be in touch with you very shortly. If you have further questions, please call us at 855.555.5555.</p>\n";
		echo "<p class='subtitle'>Have a great day!</p>\n";
		echo "</div>\n";
	} else {
		if($_GET['error_code'] == '1'){
			echo "<div class='errorBox'>\n";
			echo "<p>There is a critical errow with your form.</p>\n";
			echo "<p class='subtitle'>We apologize for the inconvienence. Please try resubmitting your data and verify it is correct. If you continue to see this message, please try again later.</p>\n";
			echo "<p class='subtitle'>Have a great day!</p>\n";
			echo "</div>\n";
		} elseif($errorFound){
			echo "<div class='errorBox'>\n";
			echo $errorReport;
			echo "</div>\n";
		} else {} ?>
		<h3 class="h3">Contact Form:</h3>
		<form action="<?=$contact_page?>" method="post" class="contactForm">
			
			<label for="firstName" class="hiddenLabel">First Name *</label>
			<input type="text" id="firstName" name="firstName" placeholder="First Name *" value="<?=$firstName?>" class="text-box-class<?php if($errorField['firstName']){echo ' error';}?>">
			
			<label for="lastName" class="hiddenLabel">Last Name *</label>
			<input type="text" id="lastName" name="lastName" placeholder="Last Name *" value="<?=$lastName?>" class="text-box-class<?php if($errorField['lastName']){echo ' error';}?>">
			
			<label for="userEmail" class="hiddenLabel">Email Address</label>
			<input type="text" id="userEmail" name="userEmail" class="text-box-class" placeholder="Email Address" value="<?=$email?>">
			
			<label for="userPhone" class="hiddenLabel">Phone Number *</label>
			<input type="text" id="userPhone" name="userPhone" placeholder="Phone Number *" value="<?=$phone?>" class="text-box-class<?php if($errorField['phone']){echo ' error';}?>">
			
			<label for="userComments" class="hiddenLabel">Comments</label>
			<textarea name="userComments" id="userComments" class="textarea" placeholder="Comments / Questions"><?=$comments?></textarea>
			<input type="submit" class="submitButton button-green" name="submit" id="submit" value="Submit">
		</form>
	<?php } ?>

</body>
</html>