使用命名空间反斜杠时如何引用数组元素？

I am trying to instantiate an object from a class, substituting an element from an array as the classname, but I keep getting PHP parse errors. I am thinking the \ character is somehow escaping the $ of the array varaiable? i.e.

$this->controller = new \app\controllers\$exploded_url[0];

gives

Parse error: syntax error, unexpected '$', expecting identifier (T_STRING)

$this->controller = new \app\controllers\${exploded_url[0]};

gives

Parse error: syntax error, unexpected '$exploded_url' (T_VARIABLE), expecting identifier (T_STRING)

How can I fix this parse error?

did you tried:

$temp = "\\app\\controllers\\".${exploded_url[0]};
$this->controller = new $temp;