


Detailed explanation of 'if statement' examples of PHP conditional control statements
if语句的作用
在所有的编程语言中,例如C语言。JAVA等,都有if语句的存在,当然也包括PHP。if语句的作用就是按照条件选择执行不同的代码片段。
我们看一下if语句的格式
if(表达式) PHP语句;
如果表达式为真的话,,那么就执行PHP语句,否则就会跳过该语句,往下执行
如果执行的语句不只一条,我们可以使用“{}”包起来,像下面这样
if(表达式){ PHP语句1; PHP语句2; PHP语句3; }
在“{}”语句我们称为语句组。
看一下if语句的控制流程
下面我们看一下if语句的示例,代码如下
<?php header("content-type:text/html;charset=utf-8"); $num=rand(1,50); if($num%2==0){ echo "\$num=$num"; echo "<br/>$num 是偶数"; } ?>
实例解释:
首先使用rand()函数生成一个1,50之间的数,然后判断这个数是不是偶数,如果是偶数,则输出结果,否则,什么也不输出。
rand()函数的作用是取得一个随机的整数。
代码运行结果:
因为是随机生成的数,有时候不是偶数的话,是不会现在出现内容的。一般遇到这种情况的时候,我们会有一个当不满足条件的时候执行的PHP语句,这就需要我们下一节的内容了,下一节,我们给大家讲PHP条件控制语句中的“if...else”语句
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