<?php

	$arrayMonths = array(
	       'jan' => array(1, 8, 5,4),
	       'feb' => array(10,12,15,11),
	       'mar' => array(12, 7, 4, 3),
	       'apr' => array(10,16,7,17),
	    );
	
	$position = array("Foo1","Foo2","Foo3","FooN");
	$set = array();
	
	foreach($arrayMonths as $key => $value)
	{
		$max = max($value);
		$pos = array_search($max, $value);
		$set[$key][$position[$pos]] = $max ;
	}
	
	
	function cmp($a, $b)
	{
		foreach($a as $key => $value )
		{
			foreach ($b  as $bKey => $bValue)
			{
				return $bValue - $value ;
			}
		}
		
	}
	
	uasort($set,"cmp");
	var_dump($set);

?>

array(4) {
  ["apr"]=>
  array(1) {
    ["FooN"]=>
    int(17)
  }
  ["feb"]=>
  array(1) {
    ["Foo3"]=>
    int(15)
  }
  ["mar"]=>
  array(1) {
    ["Foo1"]=>
    int(12)
  }
  ["jan"]=>
  array(1) {
    ["Foo2"]=>
    int(8)
  }
}