在PHP网站开发中，由于其支持各种数据库引擎，如Mysql，Mssql，Pgsql，sqlite等，并对各种数据库系统都提供了不同的函数作为接口，给PHP网站开发者带来很多便利。
但同时也带来了平台移植性的问题，随着底层数据库的改变，PHP代码也必须改变。对于这个问题，有各种解决方法，如使用PHP ADODB类，PHP PEAR DB类或者自行编写PHP DB类，将各种数据库的函数操作聚合在一起等，今天和大家分享如何安装使用PHP PEAR DB类，以实现不同数据库的访问功能。
准备工作
1、在使用PHP PEAR DB类访问数据库之前，需要安装PHP PEAR，然后通过PEAR来下载安装DB类，即pear install db
2、根据需要安装相关数据库，比如Mysql，Mssql，Pgsql，Sqlite等，同时在PHP.INI中找到Dynamic Extensions，引入对应数据的DLL文件，并重启Apache。
注意：由于我使用的是DedeAMPZ，在安装PHP PEAR时一定要安装在DedeAMPZWebRootDefault目录下，否则在引入DB.php时会报Failedopening required ‘DB.php’错误，即找不到DB类（could not find pear db library），因为DedeAMPZ可能对相关的目录做了限制。
PHP PEAR DB类使用示例
<ol class="dp-xml">
<li class="alt"><span><span class="tag"><span> ? </span></span></span></li>
<li><span>require_once("DB.php"); </span></li>
<li class="alt">
<span>$</span><span class="attribute">userName</span><span> = </span><span class="attribute-value">'root'</span><span>; </span>
</li>
<li>
<span>$</span><span class="attribute">password</span><span> = </span><span class="attribute-value">'123456'</span><span>; </span>
</li>
<li class="alt">
<span>$</span><span class="attribute">hostName</span><span> = </span><span class="attribute-value">'localhost'</span><span>; </span>
</li>
<li>
<span>$</span><span class="attribute">dbName</span><span> = </span><span class="attribute-value">'test'</span><span>; </span>
</li>
<li class="alt">
<span>$</span><span class="attribute">dsn</span><span> = </span><span class="attribute-value">"mysql://$userName:<br>$password@$hostName/$dbName"</span><span>; </span>
</li>
<li>
<span>$</span><span class="attribute">dbCon</span><span> = </span><span class="attribute-value">DB</span><span>::connect($dsn); </span>
</li>
<li class="alt"><span>if (DB::isError($dbCon)) { </span></li>
<li>
<span>die ($dbCon-</span><span class="tag">></span><span>getMessage()); </span>
</li>
<li class="alt"><span>} </span></li>
<li>
<span>$</span><span class="attribute">sql</span><span> = </span><span class="attribute-value">"CREATE TABLE leapsoul ("</span><span>. </span>
</li>
<li class="alt"><span>"`id` INT( 11 ) UNSIGNED NOT NULL ,". </span></li>
<li><span>"`name` VARCHAR( 30 ) CHARACTER <br>SET gbk COLLATE gbk_chinese_ci NOT NULL ,". </span></li>
<li class="alt"><span>"`age` INT( 2 ) NOT NULL ,". </span></li>
<li><span>"`birthday` VARCHAR( 30 ) CHARACTER <br>SET gbk COLLATE gbk_chinese_ci NOT NULL ,". </span></li>
<li class="alt"><span>"`sex` INT( 1 ) NOT NULL ,". </span></li>
<li><span>"PRIMARY KEY ( `id` )". </span></li>
<li class="alt">
<span>") </span><span class="attribute">ENGINE</span><span> = </span><span class="attribute-value">MYISAM</span><span> CHARACTER SET gbk <br>COLLATE gbk_chinese_ci"; </span>
</li>
<li>
<span>$</span><span class="attribute">result</span><span> = $dbCon-</span><span class="tag">></span><span>query($sql); </span>
</li>
<li class="alt"><span>if (DB::isError($result)) { </span></li>
<li>
<span>die ($result-</span><span class="tag">></span><span>getMessage()); </span>
</li>
<li class="alt"><span>} </span></li>
<li>
<span>$</span><span class="attribute">sql</span><span> = </span><span class="attribute-value">"insert into leapsoul(id,name,<br>age,birthday,sex) values(1,'leapsoul',1,<br>'2009-05-13',1),(2,'leapsoul',1,'2009-05<br>-13',1),(3,'leapsoul',1,'2009-05-13',1)"</span><span>; </span>
</li>
<li class="alt">
<span>$</span><span class="attribute">result</span><span> = $dbCon-</span><span class="tag">></span><span>query($sql); </span>
</li>
<li><span>if (DB::isError($result)) { </span></li>
<li class="alt">
<span>die ($result-</span><span class="tag">></span><span>getMessage()); </span>
</li>
<li><span>} </span></li>
<li class="alt">
<span>$dbCon-</span><span class="tag">></span><span>setFetchMode(DB_FETCHMODE_ASSOC); </span>
</li>
<li>
<span>$</span><span class="attribute">sql</span><span> = </span><span class="attribute-value">"select * from leapsoul"</span><span>; </span>
</li>
<li class="alt">
<span>$</span><span class="attribute">result</span><span> = $dbCon-</span><span class="tag">></span><span>query($sql); </span>
</li>
<li><span>if (DB::isError($result)) { </span></li>
<li class="alt">
<span>die ($result-</span><span class="tag">></span><span>getMessage()); </span>
</li>
<li><span>} </span></li>
<li class="alt">
<span>for($</span><span class="attribute">i</span><span>=</span><span class="attribute-value">0</span><span>;$i</span><span class="tag"><span>$result-</span><span class="tag">></span><span>numRows();$i++) </span></span>
</li>
<li><span>{ </span></li>
<li class="alt">
<span>$</span><span class="attribute">info</span><span> = &$result-</span><span class="tag">></span><span>fetchRow(); </span>
</li>
<li><span>echo "name:".$info['name']; </span></li>
<li class="alt">
<span>echo "birthday:".$info['birthday']."</span><span class="tag"><span class="tag-name">br</span><span class="tag">></span><span>"; </span></span>
</li>
<li><span>} </span></li>
<li class="alt">
<span>$result-</span><span class="tag">></span><span>free(); </span>
</li>
<li>
<span>$dbCon-</span><span class="tag">></span><span>disconnect(); </span>
</li>
<li class="alt"><span>} </span></li>
</ol>以上就是PHP PEAR DB类的详细使用方法介绍。
