Online PHP editor | refs for AXsqR

<?php $array = [ [ [ "date" => ["from_date" => "2018-07-07", "to_date" => "2018-07-07"], "post" => "Special: Pferdefotografie" ], [ "date" => ["from_date" => "2018-07-21", "to_date" => "2018-07-21"], "post" => "Fotoexkursion Südafrika" ], [ "date" => ["from_date" => "2018-07-21", "to_date" => "2018-07-21"], "post" => "Fotoexkursion Landschaftsfotografie" ], [ "date" => ["from_date" => "2018-07-21", "to_date" => "2018-07-21"], "post" => "Bildaufbau und Komposition" ], [ "date" => ["from_date" => "2018-07-22", "to_date" => "2018-07-22"], "post" => "Bildaufbau und Komposition" ] ], [ [ "date" => ["from_date" => "2018-08-11", "to_date" => "2018-08-11"], "post" => "Bildaufbau und Komposition" ], [ "date" => ["from_date" => "2018-08-04", "to_date" => "2018-08-04"], "post" => "Makrofotografie 1" ], [ "date" => ["from_date" => "2018-08-26", "to_date" => "2018-08-26"], "post" => "Tierfotografie 2" ], [ "date" => ["from_date" => "2018-08-19", "to_date" => "2018-08-19"], "post" => "Tierfotografie 1" ] ], [ [ "date" => ["from_date" => "2018-09-15", "to_date" => "2018-09-15"], "post" => "Bildaufbau und Komposition" ], [ "date" => ["from_date" => "2018-09-02", "to_date" => "2018-09-02"], "post" => "Makrofotografie 2" ], [ "date" => ["from_date" => "2018-09-01", "to_date" => "2018-09-01"], "post" => "Makrofotografie 1" ] ] ]; foreach ($array as &$set) { usort($set, function ($a, $b) { return strcmp($a['date']['from_date'], $b['date']['from_date']); }); } var_export($array);