问表单问题上的php验证

EN

 <form class="form inline d-flex justify-content-center" action="contact.php" method="POST" role="form">
             <br style="clear:both">
            <div class="col-sm-6">
              <div class="form-group">
                <input type="text" class="control" id="first_name" name="first_name" placeholder="First Name" required>
                <span class="error">* <?php echo $nameErr;?></span>
              </div>
              <div class="form-group">
                <input type="text" class="control" id="email" name="email" placeholder="Email" required>
                <span class="error">* <?php echo $emailErr;?></span>
              </div>
            </div>
            <div class="col-sm-6">
              <div class="form-group">
                <input type="text" class="control" id="last_name" name="last_name" placeholder="Last Name" required>
                <span class="error">* <?php echo $nameErr2;?></span>
              </div>
              <div class="form-group">
                <input type="text" class="control" id="phone" name="phone" placeholder="Phone" required>
                <span class="error">* <?php echo $phoneErr;?></span>
              </div>
            </div>
            <div class="col-sm-12">
              <div class="form-group">
                <textarea name="message" class="control" id="message" placeholder="What's on your mind?" rows="3"></textarea>
              </div>
              <button type="submit" id="submit" name="submit" class="btn btn-primary">SEND</button>
          </form>

<?php

if ($_SERVER["REQUEST_METHOD"] == "POST") {

    $first_name = $_POST['first_name'];
    $last_name  = $_POST['last_name'];
    $email      = $_POST['email'];
    $phone      = $_POST['phone'];
    $message    = $_POST['message'];
    $error = ''; //init error to empty string
    $pass = 0; // init pass to 0;

    if (empty($first_name)) {
        $nameErr = "First name is required";
    } else {
        $first_name = check_input($first_name);
        // check if name only contains letters and whitespace
        if (!preg_match("/^[a-zA-Z ]*$/",$first_name)) {
            $nameErr = "Only letters and white space allowed";
            $error.='<p>'.$nameErr.'</p>';

        } else {
            $pass += 1;
        }
    }

    if (empty($last_name)) {
        $nameErr2 = "Last name is required";
    } else {
        $last_name = check_input($last_name);
        // check if name only contains letters and whitespace
        if (!preg_match("/^[a-zA-Z ]*$/",$last_name)) {
            $nameErr2 = "Only letters and white space allowed";
            $error.='<p>'.$nameErr2.'</p>';
        }else {
            $pass += 1;
        }
    }

    if (empty($email)) {
        $emailErr = "Email is required";
    } else {
        $email = check_input($email);
        // check if e-mail address is well-formed
        if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
            $emailErr = "Invalid email format";
            $error.='<p>'.$emailErr.'</p>';
        }else {
            $pass += 1;
        }
    }

    if (empty($phone)) {
        $phoneErr = "Phone number is required";
    } else {
        $phone = check_input($phone);

        if (!preg_match("'^(([\+]([\d]{2,}))([0-9\.\-\/\s]{5,})|([0-9\.\-\/\s]{5,}))*$'",$phone)) {
            $phoneErr = "Invalid Phone Number";
            $error.='<p>'.$phoneErr.'</p>';
        }else {
            $pass += 1;
        }
    }

    if (empty($message)) {
        $msgErr = "Message  cannot be blank";
        $error.='<p>'.$msgErr.'</p>';
    } else {
        $message = check_input($message);
        $pass += 1;
    }
}

$email_from =' Client, llc';
$email_subject = 'New Message From A Guest';
$email_body = "Name: $first_name $last_name\n".
              "Email: $email\n".
              "Phone: $phone\n".
              "Message: $message.\n";
$to ="me@work.com";
$headers = "From: $email_from \r\n";
$headers .= "Reply-To: $email \r\n";

if ($error == '' && $pass == '5'){
    mail($to,$email_subject,$email_body,$headers);
    header("location: thanks.html");
} else {
    echo $error;
}

// purge the session after it is displayed
unset($error);

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