You could use explode, split or preg_split.

explode uses a fixed string:

$parts = explode(' ', $string);

while split and preg_split use a regular expression:

$parts = split(' +', $string);
$parts = preg_split('/ +/', $string);

An example where the regular expression based splitting is useful:

$string = 'foo   bar';  // multiple spaces
var_dump(explode(' ', $string));
var_dump(split(' +', $string));
var_dump(preg_split('/ +/', $string));

$parts = explode(" ", $str);

Just a question, but are you trying to make json out of the data? If so, then you might consider something like this:

return json_encode(explode(' ', $inputString));