I need some help learning how to pass Arrays and Variables when my Form is submitted.

Initially when my Script/Form loads, I build two arrays like this...
PHP Code:
    // Set Incoming Array Counter.
$i 1;

// Fetch record.
while (mysqli_stmt_fetch($stmt6)){
// Build All Incoming Array.
$allIncomingArray[$i] = $pmID;
$allIncomingArray[$i] . '<br />';

// Build Incoming Array.
$incomingArray[$i] = array('pmID' => $pmID,
'readOn' => $readOn,
'flag' => $flag,
'fromID' => $fromID,
'fromUsername' => $fromUsername,
'subject' => $subject,
'sentOn' => $sentOn);
$i $i 1;

(As you can see, I echoed the 1st array to the screen to confirm that it exists and has values.)

At the bottom of my script, I have my PHP/HTML which builds the Form like this...
PHP Code:
    // ****************************
    // Create 'Incoming' Output.    *
    // ****************************
echo "<h2>Incoming Messages</h2>
            <table border='1'  cellspacing='1'>
                    <!-- Header Bar -->
                        <td id='headerBar' colspan='5'>
                            <!-- Message Actions -->
                            <select name='pmAction'>
                                <option value=''>For the selected...</option>
                                <option value='In_Unread'>Mark as Unread</option>
                                <option value='In_Read'>Mark as Read</option>

                            <!-- Submit Button -->
                            <input type='submit' name='submit' value='Go'/>

<!-- LOOK HERE -->
                    <!-- Column Headings -->
                        <th class='colSelect' />
                            <input name='allIncomingArray[]' type='checkbox' value='TRUE' />
                        <th id='colFlag'>
                            <img src='/images/Flag_Red_20x22.png' width='15' alt='' />
                        <th id='colFrom'>From</th>
                        <th id='colSubject'>Subject</th>
                        <th id='colDate'>Date</th>
(As you can see in this snippet, I am trying to pass the $allIncomingArray in the <input name='allIncomingArray[]' line...)

And at the top of my script I have this code to handle the Form when it is submitted...
PHP Code:
    // ****************************************************
    // HANDLE FORM.                                     *
    // ****************************************************
// Form was Submitted (Post).

        // ****************************
        // Check for Message Action.    *
        // ****************************
if ($_POST['pmAction']=="In_Unread"){

// **************************
            // Mark Incoming as Unread.    *
            // **************************
echo var_dump($_POST['allIncomingArray']);

$allIncomingArray as $allKey => $allValue){
'$allKey = ' $allKey ', $allValue = ' $allValue '<br />';

Here is the problem...

If I choose "Mark as Read" in my drop-down, and I check the Top Check-box in the "Select" column, and then I choose "Go", I was expecting that my $allIncomingArray to get passed from my script in the $_POST array and end up being echoed to the screen as confirmation.

But instead, I get this...
0 => string 'TRUE' (length=4)

And if I just choose "Mark as Read" from my drop-down, but I do NOT check the Top Check-box, then I get this error...
Notice: Undefined index: allIncomingArray in /Users/user1/Documents/DEV/++htdocs/06_Debbie/account/messages.php on line 94
Call Stack
# Time Memory Function Location
1 0.0021 205724 {main}( ) ../messages.php:0


Can someone help me figure this out?!