JsonTable

<?php
$matrix = json_decode( $_GET[ 'jsonTable' ] );
$largestRectangle = [];
$area = 0;
for ($row = 0; $row < count( $matrix ); $row++) {
    for ($col = 0; $col < count( $matrix[ 0 ] ); $col++) {
        for ($height = 1; $height <= count( $matrix ) - $row; $height++) {
            for ($width = 1; $width <= count( $matrix[ 0 ] ) - $col; $width++) {
                if (isRect( $matrix, $row, $col, $width, $height )) {
                    if ($width * $height > $area) {
                        $area = $width * $height;
                        $largestRectangle = [ 'startRow' => $row, 'startCol' => $col,
                            'width' => $width, 'height' => $height ];
                    }
                }
            }
        }
    }
}

function isRect( $matrix, $startRow, $startCol, $width, $height) {
    $pattern = $matrix[ $startRow ][ $startCol ];
    for ($row = $startRow + 1; $row < $startRow + $height && $row < count($matrix); $row++) {
        if ($matrix[ $row ][ $startCol ] != $pattern || $matrix[ $row ][ $startCol + $width - 1 ] != $pattern) {
            return false;
        }
    }
    for ($col = $startCol + 1; $col < $startCol + $width && $col < count($matrix[0]); $col++) {
        if ($matrix[ $startRow ][ $col ] != $pattern || $matrix[ $startRow + $height - 1 ][ $col ] != $pattern) {
            return false;
        }
    }
    return true;
}

echo "<table border='1' cellpadding='5'>";
for ($row = 0; $row < count( $matrix ); $row++) {
    echo '<tr>';
    for ($col = 0; $col < count( $matrix[ 0 ] ); $col++) {
        $isTopBorder = $row == $largestRectangle[ 'startRow' ] && $col >= $largestRectangle[ 'startCol' ] &&
            $col <= $largestRectangle[ 'startCol' ] + $largestRectangle[ 'width' ] - 1;
        $isBotBorder = $row == $largestRectangle[ 'startRow' ] + $largestRectangle[ 'height' ] - 1 &&
            $col >= $largestRectangle[ 'startCol' ] && $col <= $largestRectangle[ 'startCol' ] + $largestRectangle[ 'width' ] - 1;
        $isLeftBorder = $col == $largestRectangle[ 'startCol' ] && $row >= $largestRectangle[ 'startRow' ] &&
            $row <= $largestRectangle[ 'startRow' ] + $largestRectangle[ 'height' ] - 1;
        $isRightBorder = $col == $largestRectangle[ 'startCol'] + $largestRectangle['width' ] - 1 &&
            $row >= $largestRectangle[ 'startRow' ] && $row <= $largestRectangle[ 'startRow' ] + $largestRectangle[ 'height' ] - 1;

        if ($isBotBorder || $isTopBorder || $isLeftBorder || $isRightBorder) {
            echo "<td style='background:#CCC'>";
        } else {
            echo '<td>';
        }
        echo htmlspecialchars( $matrix[ $row ][ $col ] ).'</td>';
    }
    echo '</tr>';
}
echo '</table>';