convert float to string without trim zeros in PHP [duplicate]

how can I convert $float into a string without loosing zeros on right side?

// I want to echo 44.40
$float = 44.40;

echo (string)$float; // Returns 44.4
echo strval($float); // Returns 44.4
echo "$float"; // Returns 44.4

UPDATE
I want this to works without knowing how many decimal digits there are, so using

number_format($float, 2);

is not a solution