gistfile1.php

$regions = [];

$potentialRegion = 0;

function adjacentPixelIsBlack($x, $y)
{
  if ( ! isset($matrix[$x][$y+1]))
	{
		return false;
	}

	return ($matrix[$x][$y+1] === 1);
}

// Get all of the horizontal regions
foreach ($matrix as $row => $pixels) {

	$x = $row;
	$previousBlack = 0;
	$regionStart = null;

	foreach ($pixels as $y => $colour)
	{
		// If colour is white then just continue
		if ($colour === 0)
		{
			if ($previousBlack === 1)
			{
				$regions[] = [$regionStart, [$x, $y]];
			}

			$previousBlack = 0;
			continue;
		}

		if ($previousBlack === 1)
		{
			continue;
		}
		else
		{
			$regionStart = [$x, $y];
		}
	}

}

// Convert regions which are adjacent horizontally into just one region

	// Can't work out how to do this bit