这篇随笔是对预定义数组变量的总结。通过预定义数组变量，我们可以获得系统环境、用户对话、表单数据等信息。
1.服务器变量：$_SERVER
利用foreach语句打印$_SERVER中的所有元素：
<span 1</span> <?<span php
</span><span 2</span> <span foreach</span>(<span $_SERVER</span> <span as</span> <span $key</span> => <span $value</span><span ){
</span><span 3</span> <span echo</span> <span $key</span>.' => '.<span $value</span>.'<br>'<span ;
</span><span 4</span> <span }
</span><span 5</span> ?>2.环境变量: $_ENV(无输出结果)
3.GET变量:$_GET
<span 1</span> <form action="<?<span $_SERVER</span>['PHP_SELF']?>" method="GET">
<span 2</span> 姓名:<input type="text" name="name" size="15"/>
<span 3</span> 年龄:<input type="text" name="age" size="15"/>
<span 4</span> 爱好:<input type="text" name="hobby" size="15"/>
<span 5</span> <input type="submit" name="submit" value="提交"/>
<span 6</span> </form>
<span 7</span> <?<span php
</span><span 8</span> <span if</span>(<span isset</span>(<span $_GET</span>['submit'<span ])){
</span><span 9</span> <span echo</span> '<p>'<span ;
</span><span 10</span> <span echo</span> '姓名:'.<span $_GET</span>['name'].'<br>'<span ;
</span><span 11</span> <span echo</span> '年龄:'.<span $_GET</span>['age'].'<br>'<span ;
</span><span 12</span> <span echo</span> '爱好:'.<span $_GET</span>['hobby'].'<br>'<span ;
</span><span 13</span> <span }
</span><span 14</span> ?>4.POST变量:$_POST
通过POST方式传递数据时，数据不会显示在URL中，因此相比GET方式更安全。而且，POST方式传递的数据量理论上没有限制。
<span 1</span> <form action="<?<span $_SERVER</span>['PHP_SELF']?>" method="POST">
<span 2</span> 姓名:<input type="text" name="name" size="15"/>
<span 3</span> 年龄:<input type="text" name="age" size="15"/>
<span 4</span> 爱好:<input type="text" name="hobby" size="15"/>
<span 5</span> <input type="submit" name="submit" value="提交"/>
<span 6</span> </form>
<span 7</span> <?<span php
</span><span 8</span> <span if</span>(<span isset</span>(<span $_POST</span>['submit'<span ])){
</span><span 9</span> <span echo</span> '<p>'<span ;
</span><span 10</span> <span echo</span> '姓名:'.<span $_POST</span>['name'].'<br>'<span ;
</span><span 11</span> <span echo</span> '年龄:'.<span $_POST</span>['age'].'<br>'<span ;
</span><span 12</span> <span echo</span> '爱好:'.<span $_POST</span>['hobby'].'<br>'<span ;
</span><span 13</span> <span }
</span><span 14</span> ?>5.文件上传变量:$_FILES(代码提示有误，无法找到上传文件)
<span 1</span> <form enctype="multipart/form-data" action="<?=<span $_SERVER</span>['PHP_SELF']?>" method="POST">
<span 2</span> <input type="hidden" name="MAX_FILE_SIZE" value="104857600" /><!--100M -->
<span 3</span> 上传文件:<input name="upload_file" type="file" size="50"/>
<span 4</span> <input type="submit" name="submit" value="上传" />
<span 5</span> </form>
<span 6</span> <?<span php
</span><span 7</span> <span if</span>(<span isset</span>(<span $_POST</span>['submit'<span ])){
</span><span 8</span> <span echo</span> <span $_FILES</span>['uplaod_file']['error']==UPLOAD_ERR_OK ? '上传成功!<br>': '上传失败！<br>'<span ;
</span><span 9</span> <span echo</span> '上传文件名:'.<span $_FILES</span>['upload_file']['name'].'<br>'<span ;
</span><span 10</span> <span echo</span> '上传文件大小:'.<span $_FILES</span>['upload_file']['size'].'字节<br>'<span ;
</span><span 11</span> <span echo</span> '临时文件名:'.<span $_FILES</span>['upload_file']['tmp_name'].'<br>'<span ;
</span><span 12</span> <span }
</span><span 13</span> ?>
