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HomeBackend DevelopmentPHP TutorialTips for newbies to get started with PHP (10)

建设一个简单交互的网站(六)
9. 简易banner动态更替  
  不知大家有没有发现各大站点上的标头广告banner,我们每次访问这些站点时,都会看到不同的广告图标,或者如果你每次刷新页面时,这些广告banner就会不断地随机更替变换。要实现这种效果虽然用javascript也可以达到(象天极网站的动态变换广告banner就是通过调用javascript来实现的),但是如果我们用PHP的话,我们还可以结合数据库来做数据量很大,如每日一题之类的功能。费话少说,让我们立即来看看如何用PHP来实现banner的动态更替功能。  
简易banner动态更替PHP文件(banner.php3):

//产生随机数
srand((double)microtime()*1000000);
//在0和4之间取一个数字
$randval = rand(0,5);
// 显示结果
echo "进入php的世界";
?>  
  我们可以发现,实现的程序非常简单:主要是先利用srand这一初始化随机数产生器产生随机数,再调用rand函数在定义的有效范围内来获取其中一个随机值,最后显示$randval.gif各图片banner,即0.gif、1.gif、2.gif、3.gif或4.gif。为了便于大家理解,我将rand函数的语法及相关说明罗列如下:  
rand
语法:int rand([int min], [int max]);
返回值:整数
函数种类:数学运算
内容说明:本函数用来取得随机值。若没有指定随机数的最大及最小范围,本函数会自动地从0到RAND_MAX中取一个随机数。若有指定min及max的参数,则从指定参数中取一数字。例如rand(38,49)则会从38到49之间取得一个随机值。其中UNIX系统包含49,Win32系统不包含49。值得注意的是为了使随机数的随机率最大,每次在取随机数前最好使用srand()来设定新的随机数。在本例中在用srand()来产生新的随机数时加入了时间因素,执行时以百万分之一的随机率来产生随机数
9.1 我们更改head.inc文件以应用该简易banner动态更替功能,同时还得为不同的广告banner链接到它们对应的网址。
  当然,首先我们必须先准备好用于更换交换的banner图标,同时也给我们的页面标头加上自己网站的徽标(01DC.gif)。
新的标头文件(header.inc):

// 定义通用页面头部
?>


echo "$MySiteName - $title"; ?>















Tips for newbies to get started with PHP (10)

//取得乱数种子
srand((double)microtime()*1000000);
//在0和4之间取一个数字
$randval = rand(0,5);
// 显示结果
switch($randval)
{
case "0";
echo "Tips for newbies to get started with PHP (10)";
break;
case "1";
echo "Tips for newbies to get started with PHP (10)";
break;
case "2";
echo "Tips for newbies to get started with PHP (10)";
break;
case "3";
echo "Tips for newbies to get started with PHP (10)";
break;
case "4";
echo "Tips for newbies to get started with PHP (10)";
break;
}
?>










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The above introduces the tips for newbies to get started with PHP (10), including the tips for newbies to get started. I hope it will be helpful to friends who are interested in PHP tutorials.

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