第四章_PHP基本语法

1.第一个PHP程序

<span 1</span> <span //</span><span 弱爆了有木有</span>
<span 2</span> <?<span php
</span><span 3</span>     <span echo</span> "<span Hello PHP!';
</span><span 4</span> ?>

2.PHP共支持8种基本数据理性，包括4种标量类型：boolean（布尔型）、integer（整型）、float（浮点型，也称为double）、string（字符串），2种复合类型：array（数组）、object（对象），2种特殊类型：resource（资源）、NULL（空类型）

3.函数var_dump可以用来打印变量的相关信息。

<span 1</span> <?<span php
</span><span 2</span>     <span var_dump</span>((bool) <span false</span><span );
</span><span 3</span>     <span var_dump</span>((bool) 0<span );
</span><span 4</span>     <span var_dump</span>((bool) 0.0<span );
</span><span 5</span>     <span var_dump</span>((bool) ''<span );
</span><span 6</span>     <span var_dump</span>((bool) "0"<span );
</span><span 7</span>     <span var_dump</span>((bool) <span array</span><span ());
</span><span 8</span>     <span var_dump</span>((bool) <span NULL</span><span );
</span><span 9</span> ?>

4.关于整型。

　　在32位操作系统中，整型数的有效范围是-2147483648~+2147483647。如果超过了这个范围，将会被PHP引擎解释成浮点数（float）。

　　用八进制加0，用十六进制加0x（是数字0而非字母O）

<span  1</span> <?<span php
</span><span  2</span>     <span $dec_int</span>=63<span ;
</span><span  3</span>     <span var_dump</span>(<span $dec_int</span><span );
</span><span  4</span>     
<span  5</span>     <span $oct_int</span>=077<span ;
</span><span  6</span>     <span var_dump</span>(<span $oct_int</span><span );
</span><span  7</span>     
<span  8</span>     <span $hex_int</span>=0x3f<span ;
</span><span  9</span>     <span var_dump</span>(<span $hex_int</span><span );
</span><span 10</span> ?>

5.字符串型

　　有3种定义字符串的方式，分别是单引号（‘）、双引号（“）和界定符（<<<）。前面2个的区别是，假如字符串中包含变量名，双引号中的变量名会被实际值替代，而单引号中的变量名会按普通字符直接输出。

<span 1</span> <?<span php
</span><span 2</span>     <span $name</span>='麦兜'<span ;
</span><span 3</span>     <span $age</span>=19<span ;
</span><span 4</span>     <span echo</span> '本人大名$name，年方$age'<span ;
</span><span 5</span>     <span echo</span> '<p>'<span ;
</span><span 6</span>     <span echo</span> "本人大名<span $name</span>,年方<span $age</span>"<span ;
</span><span 7</span> ?>

　　关于界定符使用如下：

<span 1</span> <?<span php
</span><span 2</span>     <span echo</span> <<<<span MY_STR
</span><span 3</span> <span     我是PHP初学者
</span><span 4</span> <span MY_STR;　　　　　　//最后结尾的标识符前面不能有空格或者缩进，必须顶咯
</span><span 5</span> ?>

6.对象类型

<span  1</span> <?<span php
</span><span  2</span> <span class</span><span  Person {
</span><span  3</span>     <span public</span> <span $name</span><span ;
</span><span  4</span>     <span private</span> <span $age</span><span ;
</span><span  5</span>     
<span  6</span>     <span function</span> Person(<span $name</span>,<span $age</span><span ){
</span><span  7</span>         <span $this</span>->name=<span $name</span><span ;
</span><span  8</span>         <span $this</span>->age=<span $age</span><span ;
</span><span  9</span> <span     }
</span><span 10</span>     
<span 11</span>     <span function</span><span  getInfo(){
</span><span 12</span>         <span echo</span> '我叫'.<span $this</span>->name.'<br>我今年'.<span $this</span>->age.'岁了'<span ;
</span><span 13</span> <span     }
</span><span 14</span> <span }
</span><span 15</span>     <span $boy</span> = <span new</span> Person("kimi",5<span );
</span><span 16</span>     <span $boy</span>-><span getInfo();
</span><span 17</span> ?>    

7.类型转换

　　print_r() 显示关于一个变量的易于理解的信息。如果给出的是 string、integer 或 float，将打印变量值本身。如果给出的是 array，将会按照一定格式显示键和元素

　　

<span  1</span> <?<span php
</span><span  2</span>     <span $temp_var</span>=3.141592653<span ;
</span><span  3</span>     <span $var1</span>=(<span string</span>)<span $temp_var</span><span ;
</span><span  4</span>     <span echo</span> "<p><span $var1</span>"<span ;
</span><span  5</span>     
<span  6</span>     <span $temp_var</span>='Kimi'<span ;
</span><span  7</span>     <span $var2</span>=(<span array</span>)<span $temp_var</span><span ;
</span><span  8</span>     <span echo</span> '<p>'<span ;
</span><span  9</span>     <span print_r</span>(<span $var2</span><span );
</span><span 10</span>     
<span 11</span>     <span $temp_var</span>='Cindy'<span ;
</span><span 12</span>     <span $var3</span>=(<span unset</span>)<span $temp_var</span><span ;
</span><span 13</span>     <span echo</span> '<p>'<span ;
</span><span 14</span>     <span var_dump</span>(<span $var3</span><span );
</span><span 15</span> ?>