【基础】PHP变量及变量作用域 - wildfox

   新学PHP，比较有意思的语法，记录下。

1. 变量的作用域

   作用域只分两个Global和Local，Global相对于整个.php文件来讲，Local是本地最小范围，是距离变量最近的范围，如：在函数中，在类中等。

2. 变量的声明

    可能是由于PHP变量独特的$符号，所以声明PHP变量不需要关键字（类中除外），第一次赋值的时候自动创建了。

    类中却比较独特了，由于类带有成员属性private、public、protected，那么在类中声明变量的时候是需要关键字修饰的。用前面所说的关键字或这个关键字var，但是不可以二者共用。

3. 样例说明

<span style="color: #008080;"> 1</span> <span style="color: #000000;">php
</span><span style="color: #008080;"> 2</span>     
<span style="color: #008080;"> 3</span>     <span style="color: #800080;">$VarFile</span> = "Var_File";   <span style="color: #008000;">//</span><span style="color: #008000;">变量声明</span>
<span style="color: #008080;"> 4</span>     
<span style="color: #008080;"> 5</span>     <span style="color: #800080;">$nr</span> = <span style="color: #0000ff;">array</span>("\n","\r","\n\r","\r\n"<span style="color: #000000;">);
</span><span style="color: #008080;"> 6</span>     
<span style="color: #008080;"> 7</span>     
<span style="color: #008080;"> 8</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> TestClass
</span><span style="color: #008080;"> 9</span> <span style="color: #000000;">{    
</span><span style="color: #008080;">10</span>     <span style="color: #008000;">/*</span>
<span style="color: #008080;">11</span> <span style="color: #008000;">    *    分别用Var声明和private关键字声明
</span><span style="color: #008080;">12</span> <span style="color: #008000;">    *   $var = value; 这种不可以
</span><span style="color: #008080;">13</span> <span style="color: #008000;">    *    var private $var; 这种不可以
</span><span style="color: #008080;">14</span> <span style="color: #008000;">    *    var private $var = value; 这种不可以
</span><span style="color: #008080;">15</span> <span style="color: #008000;">    *    var $var; 这种不可以    
</span><span style="color: #008080;">16</span>     <span style="color: #008000;">*/</span>
<span style="color: #008080;">17</span>     
<span style="color: #008080;">18</span>     <span style="color: #0000ff;">var</span> <span style="color: #800080;">$VarClass</span> = 'VarClass declared by keyword Var'<span style="color: #000000;">;            
</span><span style="color: #008080;">19</span>     <span style="color: #0000ff;">private</span> <span style="color: #800080;">$VarClass2</span> = 'VarClass2 declared by keyword private'<span style="color: #000000;">;
</span><span style="color: #008080;">20</span>     
<span style="color: #008080;">21</span>     <span style="color: #008000;">/*</span>
<span style="color: #008080;">22</span> <span style="color: #008000;">    *    增加global关键字，使用global作用域的变量
</span><span style="color: #008080;">23</span> <span style="color: #008000;">    *   函数中声明变量方法与全局一样
</span><span style="color: #008080;">24</span>     <span style="color: #008000;">*/</span>
<span style="color: #008080;">25</span>     
<span style="color: #008080;">26</span>     <span style="color: #0000ff;">function</span><span style="color: #000000;"> GetAllVar() {
</span><span style="color: #008080;">27</span>         <span style="color: #0000ff;">global</span> <span style="color: #800080;">$VarFile</span><span style="color: #000000;">;
</span><span style="color: #008080;">28</span>         <span style="color: #800080;">$VarFunction</span> = 'Var_Function'<span style="color: #000000;">;
</span><span style="color: #008080;">29</span>         
<span style="color: #008080;">30</span>         <span style="color: #800080;">$Temp</span> = "<span style="color: #800080;">$VarFile</span>=".<span style="color: #800080;">$VarFile</span>."\r\n".
<span style="color: #008080;">31</span>                 "VarClass=".<span style="color: #800080;">$this</span>->VarClass."\r\n".
<span style="color: #008080;">32</span>                 "VarClass2=".<span style="color: #800080;">$this</span>->VarClass2."\r\n".
<span style="color: #008080;">33</span>                 "VarFunction=".<span style="color: #800080;">$VarFunction</span>."\r\n"<span style="color: #000000;">;
</span><span style="color: #008080;">34</span>         
<span style="color: #008080;">35</span>         
<span style="color: #008080;">36</span>         <span style="color: #0000ff;">return</span> <span style="color: #008080;">str_replace</span>(<span style="color: #800080;">$GLOBALS</span>['nr'],"<br>",<span style="color: #800080;">$Temp</span><span style="color: #000000;">);
</span><span style="color: #008080;">37</span> <span style="color: #000000;">    }
</span><span style="color: #008080;">38</span>     
<span style="color: #008080;">39</span>     
<span style="color: #008080;">40</span> 
<span style="color: #008080;">41</span> <span style="color: #000000;">}
</span><span style="color: #008080;">42</span>     
<span style="color: #008080;">43</span>     <span style="color: #800080;">$MyClass</span> = <span style="color: #0000ff;">new</span> TestClass("zzy"<span style="color: #000000;">);
</span><span style="color: #008080;">44</span>     <span style="color: #0000ff;">echo</span> <span style="color: #800080;">$MyClass</span>-><span style="color: #000000;">GetAllVar();
</span><span style="color: #008080;">45</span>     
<span style="color: #008080;">46</span> ?>