$str = "12 34 5 6 7 890";
$strArr = explode(" ", $str);
$strArrSize = sizeof($strArr);
$allLength = 0;
$maxLength = 10;
$newStr = "";
for ($i = 0; $i < $strArrSize; $i++) {
$currLength = strlen($strArr[$i]);
if ($currLength + $allLength <= $maxLength)
{
$newStr .= $strArr[$i]." ";
}
else
{
break;
}
$allLength += $currLength + 1;
print "i=".$i."<br>";
}
if (trim($newStr) == "")
{
$newStr = substr($str, 0, $maxLength);
}
print $newStr;