How to take user input for two dimensional (2D) array in PHP ?

<?php

echo "Enter n for nxn : <br>";
echo "<form method='POST'>
    Row:<input type='number' min='2'
            max='5' name='1d' value='1'/>
    Column:<input type='number' min='2'
            max='5' name='2d' value='1'/>
    <input type='submit' name='submit'
            value='Submit'/>
</form>";

// Submit user input data for 2D array
if (isset($_POST['submit'])) {
    
    // POST submitted data
    $dimention1 = $_POST["1d"];
    
    // POST submitted data
    $dimention2 = $_POST["2d"];
    
    echo "Entered 2d nxn: " . $dimention1
            . "x" . $dimention2 . " <br>";
    $d = [];
    $k = 0;
    
    for($row = 0; $row < $dimention1; $row++) {
        for ($col = 0; $col < $dimention2; $col++) {
            $d[$row][$col]= $k++;
        }
    }
    
    for ($row = 0; $row < $dimention1; $row++) {
        for ($col = 0; $col < $dimention2; $col++) {
            echo $d[$row][$col]." ";
        }
        echo "<br>";
    }
}
?>

<?php

// fopen() using standard input
$stdin = fopen('php://stdin', 'r');
?>
<?php
error_reporting(0);
echo "\n\n\nEnter row and column: \n";

// Right trim fgets(user input) 
$dimention1 = rtrim(fgets($stdin));

// Right trim fgets(user input)
$dimention2 = rtrim(fgets($stdin));

echo "Entered row and column: " . 
    $dimention1 . "x" . $dimention1 . " \n";

$d = [];
$k = 0;

for ($row = 0; $row < $dimention1; $row++) {
    for ($col = 0; $col < $dimention2; $col++) {
        $d[$row][$col]= $k++;
    }
}

for ($row = 0; $row < $dimention1; $row++) {
    for ($col = 0; $col < $dimention2; $col++) {
        echo $d[$row][$col]." ";
    }
    echo "\n";
}

?>