I believe you're looking for the explode() function. It splits a string into an array on a specified string.
Code:
$data = "one two three four"
$result = array();
$result = explode(" ", $data);
The array $result now has the folowing values:
$result[0] = "one";
$result[1] = "two";
$result[2] = "three";
$result[3] = "four";