AA;*///1.双引号里面可以解析转义字符，单引号不行//2.双引号里面可以解析变量，单引号不行//$e = $a.$c; //拼接字符串用的是.//$f = 10.05;//$f = (string)$f; //类型转换//$f = "hello";//$aa = "cc";//$cc = "dd";//echo $$aa;  //可变变量//$dd = &$aa; //&取地址//$dd = "ee";//echo $aa;//运算符与表达式$a = 10;$b = 4;//echo $a/$b;//echo @$c; //错误抑制符，并不能抑制所有错误//echo $a==$b?"ok":"no"; //三目运算符/*if($a==$b){    echo "ok";}else{    echo "no";}*///1.if...else...//2.if...else if...//3.if嵌套/*$a = 2;switch($a){    case 1:        echo "11111";        break;    case 2:        echo "222222";        break;    case 3:        echo "333333";        break;    default:        echo "444";        break;}*///1.for/*for($i=0;$i<10;$i++){    echo $i."
";}*///2.while//3.do...while //echo $e;//var_dump($f);?>