The difference between return and Echo

The difference between return and Echo

$key = "Yongxing village to the landscape of the family";
$str = "";
     $keys =explode (' to ', $key);
             $json = @file_get_contents ("http://api.map.baidu.com/direction/v1?mode=transit&origin=". $keys [0]. " &destination= ". $keys [1]." &region= Beijing &output=json&ak=gfpnxaaipynihm7c13ez1kmel ");
             $ar = Json_decode ($json, true);
             Array_walk_recursive ($ar, ' FUNV ');
             
{
   Global $str;
               
   
   
}
return $str;

It's like, why Echo can, return not
------Solution--------------------
Big Brother, your first floor is the pattern is:
Line of code-------
Line of code-------
function---------
Line of code------
Mode of Return
Of course not, return is not in the function ah.

Your second floor pattern is: function inside the function of the pattern, or you write in the way of the class, or two functions alone, do not nest, in the main function return.
------Solution--------------------
function Funv ($v, $k)
{
...
return $str;
}


return value,
echo Display Value

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