undefined index when page is loaded

I’m having a issue where a variable is becoming undefined when the page is loaded individually… So.

My front page has a address form where when the address is filled out and you click “Get your offer” it’ll take you to another page where the address is carried over using $_POST['address'] in the value of the new input. so value="<?php echo $_POST['address']; ?>"

My problem is that when the offer page is loaded without using the front page form it gives me the error

<br /><b>Notice</b>:  Undefined index: address in <b>C:xampphtdocsofferindex.php</b> on line <b>228</b><br />Address        

which makes sense. so i tried to fix it by putting this in the value= :

<?php
                                                 $carryover = $_POST['address'] or empty($carryover); 
                                                 if(empty($carryover)) {
                                                    echo 'Enter Address';
                                                 } else {
                                                    echo $carryover;
                                                 }

                                                 ?>

which did absolutely nothing so.

Front page form:

<form method="post" action="/offer/index.php" name="front" id="front">
                                <div class="form-group">
                                    <input type="text" id="autocomplete" onFocus="geolocate()" name="address" id="address" value="" placeholder="123 main st" required>
                                    <button type="submit" class="theme-btn btn-style-nine"><span class="txt">Get your offer</span></button>
                                </div>
                            </form>

                             

Form 2 on offer page (where address is carried over too):

<form class="multisteps-form__form" action="finish.php" id="wizard" method="POST" enctype="multipart/form-data">
    <div class="col-lg-8">
                                            <div class="form-input-inner position-relative has-float-label" >
                                                <input type="text" name="address" id="address" placeholder="Address" value="<?php
                                                 $carryover = $_POST['address']; 
                                                 if(empty($carryover)) {
                                                    echo 'Address';
                                                 } else{
                                                    echo $carryover;
                                                 }

                                                 ?>

                                                 " class="form-control" required>
                                                <label>Address</label>
                                                <div class="icon-bg text-center">
                                                    <i class="fas fa-home"></i>
                                                </div>
                                            </div>
                                        </div>
</form

Answer

The undefined index notice happens when you read $_POST['address'] so any code you write after that isn’t going to affect the notice.

Checking whether $carryover is empty is too late, you need to check if the $_POST index itself is empty.

Instead of:

                                             $carryover = $_POST['address']; 
                                             if(empty($carryover)) {
                                                echo 'Enter Address';
                                             } else {
                                                echo $carryover;
                                             }

You need to use:

                                             if(empty($_POST['address']) {
                                                echo 'Enter Address';
                                             } else {
                                                $carryover = $_POST['address']; 
                                                echo $carryover;
                                             }