You may want to store a delimiting character between each set of numbers. This way you can use the explode() function so you don't have to know exactly where one substring ends and another begins. For example, let's say you choose a comma , as your delimiter, your code is:
$output='01/07/2015,21/08/2016,91754.0'; // note the addded commas
$stringParts = array();
$stringParts = explode(',' $output);
// You can now access the parts at $stringParts, $stringParts, and $stringParts.