PHP泄漏和未定义变量

Question

First time posting. I'm fairly new at this. I have experience with HTML/CSS, but not a lot with JS or PHP. I'm trying to create a contact form for my website, where users will get alerts when fields are left incomplete, and then have their information be sent to my email if everything is correct.

I used a tutorial to get most of the code, but I customized parts of it to fit my needs, and added a few repeatitive stuff.

Screenshot

However, it's not working. Or well I think it's called a PHP leak? I'm getting errors mentioning undefined variables. Anyway, here's the PHP codes, followed by the HTML.

<?php
if (isset($_POST["submit"])) {
    $name = $_POST['name'];
    $email = $_POST['email'];
    $tel = $_POST['tel'];
    $company = $_POST['companyl'];
    $message = $_POST['message'];
    $from = 'name'; 
    $to = 'johndoe@domain.com'; 
    $subject = 'company';

    $body ="From: $name\n E-Mail: $email\n Message:\n $message";
    // Check if name has been entered
    if (!$_POST['name']) {
        $errName = 'Please enter your name';
    }

    // Check if email has been entered and is valid
    if (!$_POST['email'] || !filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)) {
        $errEmail = 'Please provide us with an email address.';
    }

    //Check if phone number  has been entered
    if (!$_POST['tel']) {
        $errTel = 'Please enter a number we can reach you at.';
    }

    //Check if Company name has been entered
    if (!$_POST['company']) {
        $errCompany = 'What is the name of your company?';
    }

    //Check if message has been entered
    if (!$_POST['message']) {
        $errMessage = 'Please tell us more about your company and your needs.';
    }

    //Check if simple anti-bot test is correct
    if ($human !== 4) {
        $errHuman = 'Incorrect answer! Try again.';
    }

// If there are no errors, send the email
if (!$errName && !$errEmail && !$errMessage && !$errTel && !$errCompany && !$errHuman) {
    if (mail ($to, $subject, $body, $from)) {
        $result='<div class="alert alert-success">We will get in touch with you shortly!</div>';
    } else {
        $result='<div class="alert alert-danger">Sorry there was an error sending your message. Please try again later.</div>';
    }
}
    }
?>

HTML:

<form role="form" method="post" action="index.php">
    <div class="row">
        <div class="col-lg-6 form-group">
            <input type="text" class="formbox text-muted" id="name" name="name" placeholder="Name" required value="<?php echo htmlspecialchars($_POST['name']); ?>">
                <?php echo "<p class='text-danger'>$errName</p>";?>
        </div>
        <div class="col-lg-6 form-group">
            <input type="tel" class="formbox text-muted" id="tel" name="tel" placeholder="Phone number" required value="<?php echo htmlspecialchars($_POST['tel']); ?>">
                <?php echo "<p class='text-danger'>$errTel</p>";?>
        </div>
    </div>
    <div class="row">
        <div class="col-lg-6 form-group">
            <input type="email" class="formbox text-muted" id="email" name="email" placeholder="Email address" required value="<?php echo htmlspecialchars($_POST['email']); ?>">
            <?php echo "<p class='text-danger'>$errEmail</p>";?>

        </div>
        <div class="col-lg-6 form-group">
            <input type="text" class="formbox text-muted" id="company" name="company" placeholder="Name of your company" required value="<?php echo htmlspecialchars($_POST['company']); ?>">
            <?php echo "<p class='text-danger'>$errCompany</p>";?>
        </div>
    </div>

    <div class="row">
        <div class="col-lg-12 form-group">
                <textarea name="message" class="messagebox text-muted" id="message" name="message" placeholder="Tell us about the company you're trying to pitch" required></textarea>
        </div>
    </div>
    <div class="row">
        <div class="col-lg-6 pull-left">
            <input type="text" class="formbox text-muted" id="human" placeholder="What is is 2+2?" required value="<?php echo htmlspecialchars($_POST['human']); ?>">
            <?php echo "<p class='text-danger'>$errHuman</p>";?>
        </div>
        <div class="col-lg-4 pull-right">
            <button id=" submit" type="submit" class="inputsubmit btn btn-block btn-default btn-xl sr-button" value="send">Send Message!</button>
        </div>
        <div class="col-lg-6 pull-right">
            <?php echo $result; ?>
        </div>
    </div>
</form>

Answer 1

An easy fix: You can set all your $_POST['x'] variables to an empty string if they aren't set (don't exist), which will eliminate the undefined variable errors.

foreach( array( 'name', 'tel', 'email', 'company', 'human' ) as $key ){
    if ( !isset( $_POST[ $key ] ) ) $_POST[ $key ] = '';
}

This should be done at the top of your PHP script.

What's happening is you're trying to use the previously entered value ( $_POST['name'] ) in your HTML ( value="<?php ... ?>" ). If the user is visiting the form for the first time, they haven't provided any name, haven't posted any form data, so $_POST['name'] does not exist.

A better fix: don't output the value if it doesn't exist. Change:

<input type="text" class="formbox text-muted" id="name" name="name" placeholder="Name" required value="<?php echo htmlspecialchars($_POST['name']); ?>">

to:

<input type="text" class="formbox text-muted" id="name" name="name" placeholder="Name" required value="<?php if( isset( $_POST['name'] ) ) { echo htmlspecialchars($_POST['name']); } ?>">

Also, it appears you have a typo early on where you use companyl instead of company :

$company = $_POST['companyl'];

UPDATE You replied in your comments you're still getting undefined variables regarding error messages. You should so some similar checks here, to make sure there's an err message to echo :

<?php echo "<p class='text-danger'>$errTel</p>";?>

becomes:

<?php if( isset( $errTel ) ) { echo "<p class='text-danger'>$errTel</p>"; } ?>

(and so on, for all occurrences)

Answer 2

You should use a small inline php condition on your input value field-

<?php echo ($_POST['anything']) ? $_POST['anything'] : ''?>

The explanation is when you trying to load your page normally the $_POST is missing from the page. So just check inline if the variable exists or not. If exists then use the variable otherwise leave empty value.