php基础08：改变数据类型

<?php

    //1.获取数据类型
    $num = 55;
    echo gettype($num); //integer

    //2.设置数据类型
    settype($num, "string");
    echo "<br>";
    echo gettype($num); //string
    echo "<hr>";

    //3.isset()：判断一个变量是否存在
    $bool = isset($num); //true
    echo $bool; //1(true)
    echo "<br>";
    echo isset($num2); // 空，什么都没有

    //4.unset()：销毁一个变量
    $num3 = 50;
    unset($num3);
    echo $num3; //被销毁了
    echo "<hr>";

    //5.empty()：检测一个变量的值是否为空
    $empty1 = "";
    echo empty($empty1); //=>空字符串是 empty
    echo "<br>";

    $empty2 = 0;
    echo empty($empty2);//=>整数0是 empty
    echo "<br>";

    $empty3 = "0";
    echo empty($empty3);//=>字符串0是 empty
    echo "<hr>";

    //6.特定类型的测试函数
    $array  = array('name' => "gaoxiong" );
    echo is_array($array);
    echo "<br>";
    $float = 45.5;
    echo is_float($float);
    echo "<hr>";

    //7.临时转换类型 intval
    $sum = 22.22;
    echo $sum;
    echo "<br>";
    echo intval($sum);
    echo "<br>";
    echo $sum;
?>