it may not be possible by str_split as 'again' has 5 characters. you can get 'from', 'here' by following code.
$txt = "lookSTARTfromhereSTARTagainhere";
$txt = str_replace('look','',$txt);
$txt = str_replace('START','',$txt);
$disp = str_split($txt, 4);
for ($b = 0; $b<3; $b++) {
echo "$disp[$b]";
}
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…