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PHP语法基础，php语法_PHP教程

WBOY原创: 2016-07-12 09:05:221003浏览

PHP语法基础，php语法

1.PHP语法基础

$a = 10; 变量可以在运行过程中修改

<span>$a</span> = 10<span>;
</span><span>$a</span> = 20<span>;
</span><span>$b</span> = 5<span>;
</span><span>echo</span> <span>$a</span>+<span>$b</span>;

const THE_VALUE = 100; 常量只能被赋值一次，否则会报语法错误

<span>const</span> THE_VALUE = 100<span>;
</span><span>//</span><span>THE_VALUE = 200; 有语法错误 运行时会报错</span>
<span>echo</span> THE_VALUE;

在PHP4中定义常量的方法

<span>define</span>('THE_VALUE',200<span>);
</span><span>//</span><span>THE_VALUE = 200; 有语法错误</span>
<span>echo</span> THE_VALUE;

2.函数包装了很多功能的代码块

简单函数

<span>function</span><span> traceHelloPHP(){
    </span><span>echo</span> 'Hello PHP'<span>;
    </span><span>echo</span> '<br/>'<span>;
    </span><span>echo</span> 'Hello World'<span>;
}
traceHelloPHP();</span>

将函数作为其它函数的回调函数

<span>function</span><span> traceHelloPHP(){
    </span><span>echo</span> 'Hello PHP&mdash;&mdash;back'<span>;
    </span><span>echo</span> '<br/>'<span>;
    </span><span>echo</span> 'Hello World'<span>;
}
</span><span>//</span><span>traceHelloPHP();</span>
 
<span>$func</span> = 'traceHelloPHP'<span>;
</span><span>$func</span>();

函数的传入参数

<span>function</span> sayHello(<span>$name</span><span>){
    </span><span>echo</span> 'Hello '.<span>$name</span><span>;
    </span><span>echo</span> '<br/>'<span>;
}
sayHello(</span>'ZhangSan'<span>);
sayHello(</span>'Lisi');

多个传入参数的函数

<span>function</span> traceNum(<span>$a</span>,<span>$b</span><span>){
    </span><span>echo</span> 'a = '.<span>$a</span>.' , b = '.<span>$b</span>.'<br/>'<span>;
    </span><span>echo</span> "a = <span>$a</span> , b = <span>$b</span><br/>";  <span>//</span><span>这样写也是可以的</span>
<span>}
traceNum(</span>2,3);

带有返回值的函数

<span>function</span> add(<span>$a</span>,<span>$b</span><span>){
    </span><span>return</span> <span>$a</span>+<span>$b</span><span>;
}
</span><span>echo</span> add(10,2).'<br>';

3.流程控制

出现乱码的原因：服务器的编码方式和客户端的编码方式不同解决办法：添加html头，并将php代码嵌入body中

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Control Flow</title>
</head>
<body>
<?<span>php
</span><span>/*</span><span>*
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2015/11/10
 * Time: 16:07
 </span><span>*/</span>
<span>function</span> getLevel(<span>$score</span><span>){
    </span><span>if</span>(<span>$score</span> >= 90<span>){
        </span><span>return</span> '优秀'<span>;
    }</span><span>elseif</span>(<span>$score</span> >= 80<span>){
        </span><span>return</span> '良好'<span>;
    }</span><span>elseif</span>(<span>$score</span> >= 70<span>){
        </span><span>return</span> '好'<span>;
    }</span><span>elseif</span>(<span>$score</span> >= 60<span>){
        </span><span>return</span> '可以'<span>;
    }</span><span>else</span><span> {
        </span><span>return</span> '差'<span>;
    }
}
</span><span>echo</span> getLevel(92).'<br/>'<span>;
</span>?>
</body>
</html>

控制语句写法2

<span>function</span> getLevel_switch(<span>$score</span><span>){
    </span><span>switch</span>(<span>$score</span>/10<span>){
        </span><span>case</span> 10:
        <span>case</span> 9:
            <span>return</span> '优秀'<span>;
        </span><span>case</span> 8:
            <span>return</span> '良好'<span>;
        </span><span>case</span> 7:
            <span>return</span> '好'<span>;
        </span><span>case</span> 6:
            <span>return</span> '可以'<span>;
        </span><span>default</span>:
            <span>return</span> '差'<span>;
    }
}
</span><span>echo</span> getLevel_switch(60).'<br/>';

控制语句写法3

<span>function</span> getLevel_break(<span>$score</span><span>){
    </span><span>$result</span> = '--'<span>;
    </span><span>switch</span>(<span>intval</span>(<span>$score</span>/10<span>)){
        </span><span>case</span> 10:
        <span>case</span> 9:
            <span>$result</span> = '优秀';<span>break</span><span>;
        </span><span>case</span> 8:
            <span>$result</span> = '良好';<span>break</span><span>;
        </span><span>case</span> 7:
            <span>$result</span> = '好';<span>break</span><span>;
        </span><span>case</span> 6:
            <span>$result</span> = '可以';<span>break</span><span>;
    }
    </span><span>return</span> <span>$result</span><span>;
}
</span><span>echo</span> getLevel_break(83).'<br/>';

4.循环

for循环

<span>for</span>(<span>$i</span>=0;<span>$i</span><100;<span>$i</span>++<span>){
    </span><span>echo</span> 'Hello '.<span>$i</span>.'<br/>'<span>;
}</span>

while循环先判断再执行

<span>$i</span> = 0<span>;
</span><span>while</span>(<span>$i</span> < 50<span>){
    </span><span>echo</span> 'Hello '.<span>$i</span>.'<br/>'<span>;
    </span><span>$i</span>++<span>;
}</span>

do-while循环先执行在判断

<span>$i</span> = 0<span>;
</span><span>do</span><span>{
    </span><span>echo</span> 'Hello '.<span>$i</span>.'<br>'<span>;
    </span><span>$i</span>++;   <span>//</span><span>一定不要忘记自增，否则就会编程死循环</span>
}<span>while</span>(<span>$i</span><20);

break跳出 *整个* 循环

<span>for</span>(<span>$i</span>=0;<span>$i</span><100;<span>$i</span>++<span>){
    </span><span>echo</span> 'Hello '.<span>$i</span>.'<br/>'<span>;
    </span><span>if</span>( <span>$i</span> == 20<span> ){
        </span><span>break</span><span>;
    }
}</span>

continue 跳出 *本次* 循环

<span>for</span>(<span>$i</span>=0;<span>$i</span><100;<span>$i</span>++<span>){
    </span><span>echo</span> 'Hello '.<span>$i</span>.'<br/>'<span>;
</span><span>//</span><span>    if( $i == 20 ){
//        break;
//    }</span>
    <span>if</span>(20 == <span>$i</span><span>){
        </span><span>continue</span><span>;
    }
    </span><span>echo</span> 'Run here '.<span>$i</span>.'<br/>'<span>;
}</span>

5.逻辑运算与&& 或|| 非!

<span>function</span><span> traceNum(){
    </span><span>for</span>(<span>$i</span>=0;<span>$i</span><=100;<span>$i</span>++<span>){
</span><span>//</span><span>        if(0 == $i%2 && 0==$i%3){
//            echo $i.'<br/>';
//        }
//        if(0 == $i%2 || 0==$i%3){
//            echo $i.'<br/>';
//        }</span>
        <span>if</span>(!(0 == <span>$i</span>%2<span>)){
            </span><span>echo</span> <span>$i</span>.'<br/>'<span>;
        }
    }
}
traceNum();</span>

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