<?php
$str = "0 1 2 3 4 5 6.7 3";
function checkString($string) {
  $arr = explode(" ", $string);
  foreach($arr as $i) {
          if(!is_numeric(trim($i))) {
                  return false;
          }
  }
  return true;
}
if(checkString($str)) {
        echo "Yeah.. it works.";
}
?>