function showSelf($name="房明"){
   echo "{$name}今年十八岁<br>";
};
//函数的调用
showSelf();

if(function_exists("showSelf")){

    showSelf("盖伦");

}else{

    echo "当前函数不存在";

};

$age = 10;

function showParam1($name){

    //通过global 关键字声明当前变量是全局的

    global $age;

    $age = 20;   //此时已经将全局变量给修改

    echo $name.$age."11111<br>";

}

function showParam2($name){

    global $age;

    echo $name.$age."2222<br>";

}

showParam1("张三");

showParam2("李四");

function f1() {

    static $num = 10;

    $num++;

    echo $num."<br>";

}

f1(); //此时的结果为11

f1(); //此时的结果为12

function show() {

    echo "我被调用了<br>";

};

$f = "show";

$f();  //此时函数会被调用

function filter($f){

    for($i=0;$i<100;$i++){

        if($f($i)){

            echo $i." ";

        }

    }

};



function even($num){

    return $num%2;

};

function oven($num){

    return !($num%2);

};

filter("even");

echo "<br>";

filter("oven");