kitgrose/balanced-columns.php

## balanced-columns.php
<?php
	/*
		Makes n balanced lists of sub-lists, without breaking inside any existing lists.

		Expects input in the form:

		array(
			'Section 1' => array(
				'Item',
				'Item',
				...
			),
			'Section 2' => array(
				...
			),
			...
		)

		Returns output in the form:

		array(
			0 => array(
				'Section 1' => array(
					'Item',
					...
				),
				...
			),
			1 => array(
				'Section 2' => array(
					...
				),
				...
			),
			...
		)
	*/

	function generateRandomData($maxSections = 20, $maxItems = 20) {
		$output = array();
		for($i = 0; $i < rand(5, $maxSections); $i++) {
			for($j = 0; $j < rand(1, $maxItems); $j++) {
				$output['Section '.($i + 1)][] = 'Item '.($j + 1);
			}
		}

		return $output;
	}

	function balanceList($fullList, $numColumns = 3) {
		$totalListHeight = array_sum(array_map('count', $fullList)) + count($fullList); // Number of items plus number of sections to include headings
		$idealColumnHeight = $totalListHeight / $numColumns;

		$output = array();
		// Prime the column arrays so array_map can work
		for($i = 0; $i < $numColumns; $i++) {
			$output[$i] = array();
		}

		$currentColumn = 0;
		$listHeightRemaining = $totalListHeight;
		foreach($fullList as $title => $section) {
			$columnHeightWithSection = array_sum(array_map('count', $output[$currentColumn])) + count($section);

			if($columnHeightWithSection > $idealColumnHeight && $currentColumn !== $numColumns - 1) {
				$overflow = $columnHeightWithSection - $idealColumnHeight;

				// If the overflow of inserting this item is less than the overflow that would be caused by letting it carry over, insert it
				$expectedOverflowOnRemainingColumns = $listHeightRemaining / ($numColumns - $currentColumn - 1) - $idealColumnHeight;

				if($overflow > $expectedOverflowOnRemainingColumns) {
					$currentColumn++;
				}
			}

			$output[$currentColumn][$title] = $section;
			$listHeightRemaining -= count($section) + 1;
		}

		return $output;
	}

	$numColumns = !empty($_REQUEST['cols']) ? intval($_REQUEST['cols']) : rand(3, 5);
?>
<!DOCTYPE html>

<html lang="en">
	<head>
		<meta charset="UTF-8" />

		<style>
			#columns {
				display: table;
				width: 100%;
			}

			#columns div {
				display: table-cell;
				vertical-align: top;
			}

			h1 {
				font-size: 1em;
			}
		</style>
	</head>
	<body>
		<div id="columns">
<?php
	foreach(balanceList(generateRandomData(), $numColumns) as $column) {
?>
			<div class="column">
<?php
		foreach($column as $title => $section) {
?>
				<h1><?php echo $title; ?></h1>
				<ul>
<?php
			foreach($section as $item) {
?>
					<li><?php echo $item; ?></li>
<?php
			}
?>
				</ul>
<?php
		}
?>
			</div>
<?php
	}
?>
		</div>
	</body>
</html>
	<?php
	/*
	Makes n balanced lists of sub-lists, without breaking inside any existing lists.

	Expects input in the form:

	array(
	'Section 1' => array(
	'Item',
	'Item',
	...
	),
	'Section 2' => array(
	...
	),
	...
	)

	Returns output in the form:

	array(
	0 => array(
	'Section 1' => array(
	'Item',
	...
	),
	...
	),
	1 => array(
	'Section 2' => array(
	...
	),
	...
	),
	...
	)
	*/

	function generateRandomData($maxSections = 20, $maxItems = 20) {
	$output = array();
	for($i = 0; $i < rand(5, $maxSections); $i++) {
	for($j = 0; $j < rand(1, $maxItems); $j++) {
	$output['Section '.($i + 1)][] = 'Item '.($j + 1);
	}
	}

	return $output;
	}

	function balanceList($fullList, $numColumns = 3) {
	$totalListHeight = array_sum(array_map('count', $fullList)) + count($fullList); // Number of items plus number of sections to include headings
	$idealColumnHeight = $totalListHeight / $numColumns;

	$output = array();
	// Prime the column arrays so array_map can work
	for($i = 0; $i < $numColumns; $i++) {
	$output[$i] = array();
	}

	$currentColumn = 0;
	$listHeightRemaining = $totalListHeight;
	foreach($fullList as $title => $section) {
	$columnHeightWithSection = array_sum(array_map('count', $output[$currentColumn])) + count($section);

	if($columnHeightWithSection > $idealColumnHeight && $currentColumn !== $numColumns - 1) {
	$overflow = $columnHeightWithSection - $idealColumnHeight;

	// If the overflow of inserting this item is less than the overflow that would be caused by letting it carry over, insert it
	$expectedOverflowOnRemainingColumns = $listHeightRemaining / ($numColumns - $currentColumn - 1) - $idealColumnHeight;

	if($overflow > $expectedOverflowOnRemainingColumns) {
	$currentColumn++;
	}
	}

	$output[$currentColumn][$title] = $section;
	$listHeightRemaining -= count($section) + 1;
	}

	return $output;
	}

	$numColumns = !empty($_REQUEST['cols']) ? intval($_REQUEST['cols']) : rand(3, 5);
	?>
	<!DOCTYPE html>

	<html lang="en">
	<head>
	<meta charset="UTF-8" />

	<style>
	#columns {
	display: table;
	width: 100%;
	}

	#columns div {
	display: table-cell;
	vertical-align: top;
	}

	h1 {
	font-size: 1em;
	}
	</style>
	</head>
	<body>
	<div id="columns">
	<?php
	foreach(balanceList(generateRandomData(), $numColumns) as $column) {
	?>
	<div class="column">
	<?php
	foreach($column as $title => $section) {
	?>
	<h1><?php echo $title; ?></h1>
	<ul>
	<?php
	foreach($section as $item) {
	?>
	<li><?php echo $item; ?></li>
	<?php
	}
	?>
	</ul>
	<?php
	}
	?>
	</div>
	<?php
	}
	?>
	</div>
	</body>
	</html>