PHP Tree Structure to Html Table

Question

I have a scenario where I have a tree structure data like this:

    $tree = array(
    1 => array(
        4 => array(),
        5 => array()
    ),
    2 => array(
        6 => array(),
        7 => array(
            11 => array()
        ),
        8 => array(
            12 => array(
                14 => array(),
                15 => array()
            )
        ),
    ),
    3 => array(
        9 => array(),
        10 => array(
            13 => array()
        )
    )
);

How to create a html table using PHP recursive function like this:

1           |       2           |       3       |
4       5   |   6   7   |   8   |   9       10  |
            |       |11 |   12  |       |   13  |
                        |14 |15 |

I am using following PHP code:

function tree(array $data, &$tree = array(), $level = 0) {
    // init
    if (!isset($tree[$level])) $tree[$level] = array(count($array));

    foreach ($data as $key => $value) {

        // if value is an array, push the key and recurse through the array
        if (is_array($value)) {
            $tree[$level][] = $key;
            tree($value, $tree, $level+1);
        }
        // otherwise, push the value
        else {
           $tree[$level][] = $value;
        }
    }
}

function make_table($array)
{
    $output = '';
    foreach($array as $item => $tr)
    {
        $c = 100/count($tr);
        $output .= "<tr>";

        foreach($tr as $th => $val)
        {           
            $output .= "<th style='width:" . $c . "%'>" . $val . "</th>";
        }

        $output .= "</tr>";     
    }

    return $output;
}

But the above code does not handle empty space like in third row of first column.

1 | 2 | 3 |
4 | 5 | 6 | 7 | 8 | 9 | 10 |
11 | 12 | 13 |
14 | 15 |

It will be easy if you can convert that array to a two dimentional array with fixed number of columns. — Subin Thomas
– Subin Thomas, Commented Aug 28, 2015 at 12:55
It would be easier to do an complete tree, rather than one with empty leaves, because the number of columns of an element would be known at any given time. The elements without a value could be left blank then. — syck
– syck, Commented Aug 28, 2015 at 13:08

chocochaos · Accepted Answer · 2016-06-08 16:14:42Z

You need some way to keep track of colspans and the position of every cell in the table, and then fill the gaps with empty cells.

I wrote this today, it seems to work fine for your example:

<?php

$tree = [
    'Table Title' => [
        1 => [
            4 => [],
            5 => []
        ],
        2 => [
            6 => [],
            7 => [
                11 => []
            ],
            8 => [
                12 => [
                    14 => [],
                    15 => []
                ]
            ],
        ],
        3 => [
            9  => [],
            10 => [
                13 => []
            ]
        ]
    ]
];

// Loop over the tree. Every leaf in the root of the tree
// gets his own table(s).
foreach ($tree as $name => $leaves) {
    $table = [];
    parseLeaf($name, $leaves, $table);
    $table = cleanupRows($table);

    output($table);
}

/**
 * Convert a leaf in the tree to an array to be used to print the tables.
 * The span of a leaf is either the sum of its children's spans,
 * or 1 if it has no children.
 *
 * @param string $name
 * @param array  $leaves
 * @param array  $table
 * @param int    $level
 * @param int    $position
 *
 * @return int
 */
function parseLeaf($name, $leaves, &$table, $level = 0, $position = 0)
{
    if (!empty($leaves)) {
        $span = 0;

        foreach ($leaves as $leafName => $childLeaves) {
            $span += parseLeaf(
                $leafName,
                $childLeaves,
                $table,
                $level + 1,
                $position + $span
            );
        }
    } else {
        $span = 1;
    }

    $table[$level][$position] = getCell($name, $span);;

    return $span;
}

/**
 * Insert empty cells where needed and sort by keys.
 *
 * @param array $table
 *
 * @return array
 */
function cleanupRows($table)
{
    $width = $table[0][0]['span'];

    foreach ($table as $rowNumber => $row) {
        $spanSoFar = 0;
        foreach ($row as $position => $cell) {
            addExtraCells($table, $spanSoFar, $rowNumber, $position);
            $spanSoFar += $cell['span'];
        }
        addExtraCells($table, $spanSoFar, $rowNumber, $width);
        ksort($table[$rowNumber]);
    }
    ksort($table);

    return $table;
}

/**
 * @param array $table
 * @param int   $spanSoFar
 * @param int   $rowNumber
 * @param int   $position
 */
function addExtraCells(&$table, &$spanSoFar, $rowNumber, $position)
{
    while ($spanSoFar < $position) {
        $table[$rowNumber][$spanSoFar] = getCell();
        $spanSoFar += 1;
    }
}

/**
 * @param string $name
 * @param int    $span
 *
 * @return array
 */
function getCell($name = '', $span = 1)
{
    return ['name' => $name, 'span' => $span];
}

/**
 * Print the table.
 *
 * @param array $table
 */
function output($table)
{
    echo '<table border="1">';
    foreach ($table as $row) {
        echo '<tr>';
        foreach ($row as $cell) {
            echo '<td colspan="' . $cell['span'] . '" align="center">';
            echo $cell['name'];
            echo '</td>';
        }
        echo '</tr>';
    }
    echo '</table>';
}

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