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POUsing usort to sort Arrays of Arrays with Arrays PHP
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  1. POUsing usort to sort Arrays of Arrays with Arrays PHP
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    copied!<p>I have an array of arrays with arrays in PHP and I want to sort the top level of the array based on a field within each element, and I also want to sort an array within each element based on an element of an array of that element. (see example). I want it so that in the end, <code>$data</code> has first the item with the <code>'primary'</code> value of 'first' then 'second'. I also want it so that within 'first' and 'second', the array under the field <code>'secondary'</code> has first the item with the <code>'val'</code> of 'foo' then 'bar' (for both 'first' and 'second') </p> <pre><code>$data = array ( array ( 'myid' =&gt; 4, 'primary' =&gt; 'second', 'secondary' =&gt; array ( array ( 'myid' =&gt; 10, 'val' =&gt; 'bar', ), array ( 'myid' =&gt; 8, 'val' =&gt; 'foo', ), ), ), array ( 'myid' =&gt; 2, 'primary' =&gt; 'first', 'secondary' =&gt; array ( array ( 'myid' =&gt; 10, 'val' =&gt; 'bar', ), array ( 'myid' =&gt; 8, 'val' =&gt; 'foo', ), ), ), ); function mysort($a, $b) { return $a['myid'] &gt; $b['myid']; } echo "pre sort:\n"; print_r($data); usort($data, 'mysort'); echo "post top level sort:\n"; print_r($data); foreach ($data as $k=&gt;$item) { usort($item['secondary'], 'mysort'); echo "Second Level Item sort:\n"; print_r($item['secondary']); } echo "post second level sort:\n"; print_r($data); </code></pre> <p>Why am I getting the following final output?</p> <pre><code>post second level sort: Array ( [0] =&gt; Array ( [myid] =&gt; 2 [primary] =&gt; first [secondary] =&gt; Array ( [0] =&gt; Array ( [myid] =&gt; 10 [val] =&gt; bar ) [1] =&gt; Array ( [myid] =&gt; 8 [val] =&gt; foo ) ) ) [1] =&gt; Array ( [myid] =&gt; 4 [primary] =&gt; second [secondary] =&gt; Array ( [0] =&gt; Array ( [myid] =&gt; 10 [val] =&gt; bar ) [1] =&gt; Array ( [myid] =&gt; 8 [val] =&gt; foo ) ) ) ) </code></pre> <p>By the way I'm using PHP 5.2.17.</p>
 

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