Tic Tac Toe

<html>
<head>
<title> PHP Tic Tac Toe</title>
</head>
<body>
<?php
//Variables
//Boxes numbers in book-like order

//The user input
$value = $_POST['value'];

//If the user hasn't hit submit, the boxes will be empty
if(!isset($_POST['submit'])){
    $box1 = '-';
    $box2 = '-';
    $box3 = '-';
    $box4 = '-';
    $box5 = '-';
    $box6 = '-';
    $box7 = '-';
    $box8 = '-';
    $box9 = '-';
}else{
    $box1 = $_POST['box1'];
    $box2 = $_POST['box2'];
    $box3 = $_POST['box3'];
    $box4 = $_POST['box4'];
    $box5 = $_POST['box5'];
    $box6 = $_POST['box6'];
    $box7 = $_POST['box7'];
    $box8 = $_POST['box8'];
    $box9 = $_POST['box9'];

}

//Read user input and act accordingly
if(isset($_POST['submit'])){
    if($value == 'box1'){
        $box1 = 'X';
    }
    if($value == 'box2'){
        $box2 = 'X';
    }
    if($value == 'box3'){
        $box3 = 'X';
    }
    if($value == 'box4'){
        $box4 = 'X';
    }
    if($value == 'box5'){
        $box5 = 'X';
    }
    if($value == 'box6'){
        $box6 = 'X';
    }
    if($value == 'box7'){
        $box7 = 'X';
    }
    if($value == 'box8'){
        $box8 = 'X';
    }
    if($value == 'box9'){
        $box9 = 'X';
    }
}

echo '<table border="1px">';
echo '<tr>';
echo '<td>'.$box1.'</td>';
echo '<td>'.$box2.'</td>';
echo '<td>'.$box3.'</td>';
echo '</tr>';
echo '<tr>';
echo '<td>'.$box4.'</td>';
echo '<td>'.$box5.'</td>';
echo '<td>'.$box6.'</td>';
echo '</tr>';
echo '<tr>';
echo '<td>'.$box7.'</td>';
echo '<td>'.$box8.'</td>';
echo '<td>'.$box9.'</td>';
echo '</tr>';
echo '</table>';
?>
<br>
<form method='POST' action='<?php echo $_SERVER['PHP_SELF'];?>'>
    <input type='text' name='value'>
    <input type='hidden' value= "<?php echo $turn;?>" name='turn'>
    <input type='hidden' value= "<?php echo $box1;?>" name='box1'>
    <input type='hidden' value= "<?php echo $box2;?>" name='box2'>
    <input type='hidden' value= "<?php echo $box3;?>" name='box3'>
    <input type='hidden' value= "<?php echo $box4;?>" name='box4'>
    <input type='hidden' value= "<?php echo $box5;?>" name='box5'>
    <input type='hidden' value= "<?php echo $box6;?>" name='box6'>
    <input type='hidden' value= "<?php echo $box7;?>" name='box7'>
    <input type='hidden' value= "<?php echo $box8;?>" name='box8'>
    <input type='hidden' value= "<?php echo $box9;?>" name='box9'>
    <input type="submit" value="Turn" name="submit">
</form>
</body>
</html>