Isset($_POST['submit) is not working - php

Question

Isset($_POST['submit) is not working but when I add the not operation(!) it worked. i don't where to find the error.
here is my code
$get = isset($_GET['id']) ? $_GET['id'] : "";
$query = "SELECT * FROM `crew_info` WHERE `id` = '$get'";
$query_run = mysqli_query($conn,$query);
if(!isset($_POST['submit'])) {
$query_update = "UPDATE `crew_info` SET `crew_status` = 'NEW' WHERE `id` = '$get'";
if ($query_update_run = mysqli_query($conn,$query_update)) {
echo 'Crew Accepted';
}
}
here is the submit form
<form action="review.php" method="POST">
<table border="2" align="center" width="600" cellspacing="3" cellpadding="4">
<tr>
<th>First Name</th>
<th>Middle Name</th>
<th>Last Name</th>
<th>Date Added</th>
<th>Status</th>
</tr>
<tr>';
while($record = mysqli_fetch_assoc($query_run)) {
echo "<tr>";
echo "<th>".$record['first_name']."</th>";
echo "<th>".$record['middle_name']."</th>";
echo "<th>".$record['last_name']."</th>";
echo "<th>".$record['date_added']."</th>";
echo "<th>".$record['crew_status']."</th>";
echo '</tr>';
}
echo '</table>';
echo '<br><center><input type="submit" name="submit"></center>
</form>

Answer 1

You are not submitting any values.
<input type="submit" name="submit">
Try something like this:
<input type="submit" name="submit" value="ok">
This piece of PHP checks if the form element with the name "submit" has any value:
"if isset($_POST['submit'])"
But since you haven't set any value for "submit", it won't validate. However, it will validate when you set the exclamation mark in front of it:
!if isset($_POST['submit'])"
This is because then you are saying, "if 'submit' has no value set, do the following".
Hope that makes sense. :)
Update: You also have several other errors that you need to fix to get the whole thing working. This should fix most of it. Compare it to your current code:
<?php $get = isset($_GET['id']) ? $_GET['id'] : "";
$query = "SELECT * FROM crew_info WHERE id = '$get'";
$query_run = mysqli_query($conn,$query);
if(isset($_POST['submit'])) {
$query_update = "UPDATE crew_info SET crew_status = 'NEW' WHERE id = '$get'";
if ($query_update_run = mysqli_query($conn,$query_update)) {
echo 'Crew Accepted';
}
} ?>
<form action="review.php" method="POST">
<table border="2" align="center" width="600" cellspacing="3" cellpadding="4">
<tr>
<th>First Name</th>
<th>Middle Name</th>
<th>Last Name</th>
<th>Date Added</th>
<th>Status</th>
</tr>
<tr>
<?php
while($record = mysqli_fetch_assoc($query_run)) {
echo "<tr>";
echo "<th>".$record['first_name']."</th>";
echo "<th>".$record['middle_name']."</th>";
echo "<th>".$record['last_name']."</th>";
echo "<th>".$record['date_added']."</th>";
echo "<th>".$record['crew_status']."</th>";
echo '</tr>';
}
echo '</table>';
echo '<br><center><input type="submit" name="submit" value="ok"></center>';
?>
</form>