PHP中的if else 和elseif and else if

//if语句书写
 $b)
  echo "a is bigger than b";
?>

//else语句的书写
 $b) {
  echo "a is greater than b";
} else {
  echo "a is NOT greater than b";
}
?>

//elseif/else if语句书写
 $b) {
    echo "a is bigger than b";
} elseif ($a == $b) {
    echo "a is equal to b";
} else {
    echo "a is smaller than b";
}
?>