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POConvert a series of parent-child relationships into a tree?
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  1. POConvert a series of parent-child relationships into a tree?
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    copied!<p>I am terribly stuck. I think I need to write a recursive method but I can't work out how...!</p> <p>I am trying to convert an array of parent-child relationships into a hierarchical tree which I will later display to a user.</p> <p>This is an example of the input data I might have:</p> <pre><code>$input = array( array( 'itemGroupID' =&gt; 1, 'childItemGroupID' =&gt; 2 ), array( 'itemGroupID' =&gt; 1, 'childItemGroupID' =&gt; 3 ), array( 'itemGroupID' =&gt; 1, 'childItemGroupID' =&gt; 4 ), array( 'itemGroupID' =&gt; 1, 'childItemGroupID' =&gt; 212 ), array( 'itemGroupID' =&gt; 1, 'childItemGroupID' =&gt; 339 ), array( 'itemGroupID' =&gt; 1, 'childItemGroupID' =&gt; 336 ), array( 'itemGroupID' =&gt; 1, 'childItemGroupID' =&gt; 6 ), array( 'itemGroupID' =&gt; 1, 'childItemGroupID' =&gt; 5 ), array( 'itemGroupID' =&gt; 6, 'childItemGroupID' =&gt; 8 ), array( 'itemGroupID' =&gt; 6, 'childItemGroupID' =&gt; 9 ), array( 'itemGroupID' =&gt; 6, 'childItemGroupID' =&gt; 10 ), array( 'itemGroupID' =&gt; 6, 'childItemGroupID' =&gt; 11 ), array( 'itemGroupID' =&gt; 6, 'childItemGroupID' =&gt; 12 ), array( 'itemGroupID' =&gt; 6, 'childItemGroupID' =&gt; 13 ), array( 'itemGroupID' =&gt; 6, 'childItemGroupID' =&gt; 74 ), array( 'itemGroupID' =&gt; 9, 'childItemGroupID' =&gt; 15 ), array( 'itemGroupID' =&gt; 10, 'childItemGroupID' =&gt; 16 ), array( 'itemGroupID' =&gt; 11, 'childItemGroupID' =&gt; 17 ), array( 'itemGroupID' =&gt; 12, 'childItemGroupID' =&gt; 18 ), array( 'itemGroupID' =&gt; 13, 'childItemGroupID' =&gt; 19 ), array( 'itemGroupID' =&gt; 74, 'childItemGroupID' =&gt; 75 ) ); </code></pre> <p>I wish to get back data in a format like:</p> <pre><code>$output = array( array( 'itemGroupID' =&gt; 1, 'children' =&gt; array( array( 'itemGroupID' =&gt; 2 ), array( 'itemGroupID' =&gt; 3 ), array( 'itemGroupID' =&gt; 4 ), array( 'itemGroupID' =&gt; 212 ), array( 'itemGroupID' =&gt; 339 ), array( 'itemGroupID' =&gt; 336 ), array( 'itemGroupID' =&gt; 6, 'children' =&gt; array( array( 'itemGroupID' =&gt; 8 ), array( 'itemGroupID' =&gt; 9, 'children' =&gt; array( array( 'itemGroupID' =&gt; 15 ) ) ), array( 'itemGroupID' =&gt; 10, 'children' =&gt; array( array( 'itemGroupID' =&gt; 16 ) ) ), array( 'itemGroupID' =&gt; 11, 'children' =&gt; array( array( 'itemGroupID' =&gt; 17 ) ) ), array( 'itemGroupID' =&gt; 12, 'children' =&gt; array( array( 'itemGroupID' =&gt; 18 ) ) ), array( 'itemGroupID' =&gt; 13, 'children' =&gt; array( array( 'itemGroupID' =&gt; 19 ) ) ), array( 'itemGroupID' =&gt; 74, 'children' =&gt; array( array( 'itemGroupID' =&gt; 75 ) ) ) ) ), array( 'itemGroupID' =&gt; 5 ) ) ) ); </code></pre> <p>I managed to write some code which would tell me the root(s) to start from. (As I was worried that if you were recursing from the first node it might turn out that this is from half-way down the chain already...)</p> <p>Btw, the element I output can be used to get the starting index, for each hierarchical chain.</p> <pre><code>private function _arraySearch($arr, $callback) { foreach ($arr as $key =&gt; $item) { if ($callback($item)) { return $key; } } return false; } private function _findRootsOfItemGroupTree($activeItemGroupChildren) { $searchArray = $activeItemGroupChildren; $roots = array(); foreach ($activeItemGroupChildren as $itemGroupChild) { $parentItemGroupID = $itemGroupChild['itemGroupID']; $found = array_filter($searchArray, function ($element) use ($parentItemGroupID) { return $element['childItemGroupID'] == $parentItemGroupID; }); $rootItemGroupID = $parentItemGroupID; if (count($found) == 0 &amp;&amp; $this-&gt;_arraySearch($roots, function ($element) use ($rootItemGroupID) { return $element['itemGroupID'] == $rootItemGroupID; }) === false) { $roots[] = $itemGroupChild; } } return $roots; } </code></pre> <p>However, I now need to use this information to create a new associative array. I can't work out how. (I will post some workings in a couple of minutes..)</p> <p>Ideas?</p> <p>note: assume there are no recursive loops in this structure even though they could technically exist.</p>
 

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