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<h1>CAPTCHA 辅助函数</h1>

<p>验证码辅助函数用来生成图片验证码</p>


<h2>加载辅助函数</h2>

<p>用下面的代码加载验证码辅助函数:</p>
<code>$this-&gt;load-&gt;helper('captcha');</code>

<p>可用的函数如下：</p>

<h2>create_captcha(<var>$data</var>)</h2>

<p>根据你指定的一系列参数创建验证码图像, 返回值是一个包含此图像数据的数组.</p>

<code>[array]<br />
(<br />
&nbsp;&nbsp;'image' => IMAGE TAG<br />

&nbsp;&nbsp;'time'  => TIMESTAMP (毫秒)<br />
&nbsp;&nbsp;'word'  => CAPTCHA WORD<br />
)</code>

  <p>"image"是实际存在image标记:
<code>&lt;img src=&quot;http://example.com/captcha/12345.jpg&quot; width=&quot;140&quot; height=&quot;50&quot; /&gt;</code></p>

  <p>这里的"time"是一个毫秒级的时间戳，作为图片文件名（不包含扩展名）. 就像这样:  1139612155.3422</p>

  <p>"word"是验证码, 如果不提供, 将是一个随机字符串.</p>

  <h3>使用验证码辅助函数：</h3>

  <p>加载后你可以向这样产生一个验证码:</p>

<code>$vals = array(<br />
&nbsp;&nbsp;&nbsp;&nbsp;'word'     => 'Random word',<br />
&nbsp;&nbsp;&nbsp;&nbsp;'img_path'   => './captcha/',<br />
&nbsp;&nbsp;&nbsp;&nbsp;'img_url'   => 'http://example.com/captcha/',<br />
&nbsp;&nbsp;&nbsp;&nbsp;'font_path'   => './path/to/fonts/texb.ttf',<br />
&nbsp;&nbsp;&nbsp;&nbsp;'img_width'   => '150',<br />
&nbsp;&nbsp;&nbsp;&nbsp;'img_height' => 30,<br />
&nbsp;&nbsp;&nbsp;&nbsp;'expiration' => 7200<br />
&nbsp;&nbsp;&nbsp;&nbsp;);<br />

<br />
$cap = create_captcha($vals);<br />
echo $cap['image'];</code>

  <ul>
    <li>验证码辅助函数必须需要GD库.</li>
    <li>只有 img_path 和 img_url 参数是必须的.</li>
    <li>如果"word"未提供, 将自动产生一个ASCII字符串.  你也可以使用自己的词库，从里面随机挑选.</li>

    <li>如果未提供TRUE TYPE字体的路径, 将会使用GD自带的字体.</li>
    <li> "captcha" 目录必须可写(666, or 777)</li>
    <li>"expiration" (秒) 指定了验证码图片的超时删除时间.  默认是2小时.</li>
  </ul>

  <h3>配合数据库</h3>

  <p>为了在提交表单时用到验证，你需要将<kbd>create_captcha()</kbd>生成的结果保存到数据库。这样，当用户提交表单时，你就可以验证数据库里是否有此验证码或是否过期。</p>

  <p>这是一个数据表的例子:</p>

<code>CREATE TABLE captcha (<br />
&nbsp;captcha_id bigint(13) unsigned NOT NULL auto_increment,<br />
&nbsp;captcha_time int(10) unsigned NOT NULL,<br />
&nbsp;ip_address varchar(16) default '0' NOT NULL,<br />
&nbsp;word varchar(20) NOT NULL,<br />
&nbsp;PRIMARY KEY `captcha_id` (`captcha_id`),<br />

&nbsp;KEY `word` (`word`)<br />
);</code>

  <p>这是一个使用数据库的例子.  一个带验证码的页面显示如下:</p>

<code>$this-&gt;load-&gt;helper(&#x27;captcha&#x27;);<br />
$vals = array(<br />

&nbsp;&nbsp;&nbsp;&nbsp;&#x27;img_path&#x27;   =&gt; &#x27;./captcha/&#x27;,<br />
&nbsp;&nbsp;&nbsp;&nbsp;&#x27;img_url&#x27;   =&gt; &#x27;http://example.com/captcha/&#x27;<br />
&nbsp;&nbsp;&nbsp;&nbsp;);<br />
<br />
$cap = create_captcha($vals);<br />

<br />
$data = array(<br />
&nbsp;&nbsp;&nbsp;&nbsp;&#x27;captcha_time&#x27;  =&gt; $cap[&#x27;time&#x27;],<br />
&nbsp;&nbsp;&nbsp;&nbsp;&#x27;ip_address&#x27;  =&gt; $this-&gt;input-&gt;ip_address(),<br />

&nbsp;&nbsp;&nbsp;&nbsp;&#x27;word&#x27;      =&gt; $cap[&#x27;word&#x27;]<br />
&nbsp;&nbsp;&nbsp;&nbsp;);<br />
<br />
$query = $this-&gt;db-&gt;insert_string(&#x27;captcha&#x27;, $data);<br />

$this-&gt;db-&gt;query($query);<br />
<br />
echo &#x27;提交下面的验证码:&#x27;;<br />
echo $cap[&#x27;image&#x27;];<br />
echo &#x27;&lt;input type=&quot;text&quot; name=&quot;captcha&quot; value=&quot;&quot; /&gt;&#x27;;</code>

  <p>然后页面提交后如下处理:</p>

<code>// 首先删除旧的验证码<br />
$expiration = time()-7200; // 2小时限制<br />
$this-&gt;db-&gt;query(&quot;DELETE FROM captcha WHERE captcha_time &lt; &quot;.$expiration);  <br />
<br />

// 然后再看是否有验证码存在:<br />
$sql = &quot;SELECT COUNT(*) AS count FROM captcha WHERE word = ? AND ip_address = ? AND captcha_time &gt; ?&quot;;<br />
$binds = array($_POST[&#x27;captcha&#x27;], $this-&gt;input-&gt;ip_address(), $expiration);<br />
$query = $this-&gt;db-&gt;query($sql, $binds);<br />

$row = $query-&gt;row();<br />
<br />
if ($row-&gt;count == 0)<br />
&#123;<br />
&nbsp;&nbsp;&nbsp;&nbsp;echo &quot;你必须提交图像上显示的验证码&quot;;<br />
&#125;</code><p>&nbsp;</p>
<div id="Contributors">
翻译贡献者:
CosyBoy, Hex, LSvKing, 杜建宇</div>
<div id="DocDate">
最后修改: 2012-02-05 23:50:26</div>
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