- var_dump: documentation ( source)
- json_decode: documentation ( source)
- array_reduce: documentation ( source)
- json_encode: documentation ( source)
<?php
$a = json_encode(array('sleep' => 123));
$b = json_encode(array('sleep' => 987));
$logs = array(array('date' => '2014-01-01', 'data' => $a), array('date' => '2015-01-01', 'data' => $b));
$result = array_reduce($logs, function ($cur, $x) {
$data = json_decode($x['data']);
$cur[$x['date']] = $data->{'sleep'};
return $cur;
}, array());
var_dump($result);