PHP：Echo没有从表单上处理POST方法

Question

I am a bit new to PHP and I'm having a bit of difficulties here and there. I am developing a form and wish to display an error box if any of the fields are empty when the 'Submit' Button is pressed. I've tried the following code but the echo is still not appearing. Any suggestions ?

Form Code:

<div style="padding-top:40px">
    <div style="text-center; padding-right:25%; padding-left:25%">
        <div class="form-area">  
            <form role="form" method="$_POST" action="searchEmployee.php">
            <br style="clear:both">
                <h3 style="margin-bottom:25px; text-align: center;">Visitor Form</h3>
                <div class="form-group">
                    <label>Name:</label>
                    <input type="text" class="form-control" id="name" name="name" placeholder="Name" required>
                </div>
                <div class="form-group">
                     <label>Surname:</label>
                    <input type="text" class="form-control" id="surname" name="surname" placeholder="Surname" required>
                </div>
                <div class="form-group">  
                    <label>ID Card:</label>
                    <input type="text" class="form-control" id="idCard" name="idCard" placeholder="ID Card No" required>
                </div>
                <div class="form-group">  
                    <label>Visitor Card Number:</label>
                    <input type="text" class="form-control" id="cardNumber" name="cardNumber" placeholder="Card No" required>
                </div>
                <div class="form-group">  
                    <intput type="button" id="submit" name="submit" class="btn btn-primary pull-right">Sign In Visitor</button>
                </div>
            </form>
        </div>
    </div>
</div>

PHP Code:

<?php
        if (isset($_POST['submit'])) {
            $required = array('name', 'surname', 'ID', 'visitorCard');

            // Loop over field names, make sure each one exists and is not empty
            $error = false;
            foreach($required as $field) {
                if (empty($_POST[$field])) {
                $error = true;
                }
            }

            if ($error) {
                echo "All fields are required.";
            }
        }
        ?>

Answer 1

Here are few mistakes:

1. You are using method as $_POST in your form attribute, It should be only POST.

2. Your form will not submit because your button is not a submit type. it should

   <input type="submit" id="submit" name="submit" class="btn btn-primary pull-right" value="Sign In Visitor" />
   

   Or

   <button type="submit" id="submit" name="submit" class="btn btn-primary pull-right">Sign In Visitor</button>