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——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>

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。


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