关于PEAR DB的使用

 通过 Pear DB可以从查询结果获得更多有用的数据信息 。这些方法有:
numRows(): 通过一个"SELECT" 查询返回所有数据的数量。
numCols():通过一个"SELECT" 查询返回所有的列。
affectedRows(): 通过("INSERT", "UPDATE" or "DELETE")操作返回所有受影响的数据行数。
tableInfo():通过一个"SELECT" 查询返回一个包含数据信息的数组。

可用方法列表：

<?php
 /*
 * From the DB_(driver) objects
 */
 // get the object with, ie:
 $db = DB::connect('mysql://user:pass@localhost/my_db');
  
 // Set options
 $db->setErrorHandling();
 $db->setFetchmode();
 // Information
 $db->affectedRows();
 $db->tableInfo();
 // Database manipulation
 $db->query();
 // Data fetch
 $db->nextId();
 $db->getOne();
 $db->getRow();
 $db->getCol();
 $db->getAssoc();
 $db->getAll();
 // Place holders and execute related
 $db->quote();
 $db->prepare();
 $db->execute();
 $db->executeMultiple();
 // Transactions
 $db->autoCommit();
 $db->commit();
 $db->rollback();
 // Disconnection
 $db->disconnect();
  
 /*
 * From DB_result objects
 */
 // get the object with, ie: 
 $res = $db->query('select * from foo');
  
 // Data fetch
 $res->fetchRow();
 $res->fetchInto();
 // Result Info
 $res->numCols();
 $res->numRows();
 $res->tableInfo();
 // Free
 $res->free();
  
 /*
 * From DB_error objects
 */
 // get the object with, ie:
 $error = $db->query('select * from no_table');
  
 $error->getMessage();
 $error->getDebugInfo();
 $error->toString();
 ?>

//////////////////////////////////////////////
///其他详细使用
///////////////////////////////////////////////
PEAR DB 的连接和断开

<?php
 // The pear base directory must be in your include_path
 require_once 'DB.php';
 $user = 'foo';
 $pass = 'bar';
 $host = 'localhost';
 $db_name = 'clients_db';
 
 // Data Source Name: This is the universal connection string
 $dsn = "mysql://$user:$pass@$host/$db_name";
 
 // DB::connect will return a Pear DB object on success
 // or a Pear DB Error object on error
 // You can also set to TRUE the second param
 // if you want a persistent connection:
 // $db = DB::connect($dsn, true);
 $db = DB::connect($dsn);
 
 // With DB::isError you can differentiate between an error or
 // a valid connection.
 if (DB::isError($db)) {
         die ($db->getMessage());
 }
 ....
 // You can disconnect from the database with:
 $db->disconnect();
 ?>
=======================

执行数据库并获得数据
<?php
 // Once you have a valid DB object
 ...
 $sql = "select * from clients";
 // If the query is a "SELECT", $db->query will return
 // a DB Result object on success.
 // Else it simply will return a DB_OK
 // On failure it will return a DB Error object.
 $result = $db->query($sql);
 // Always check that $result is not an error
 if (DB::isError($result)) {
         die ($result->getMessage());
 }
 
 // Once you have a valid DB Result object
 ...
 // Get each row of data on each iteration until
 // there is no more rows
 while ($row = $result->fetchRow()) {
     $id = $row[0];
 }
 
 ?>

===============================
选择获取数据的格式
<?php
 $res = $db->query('select id, name, email from users');
 $row = $res->fetchRow($mode);
 
 //With $mode = DB_FETCHMODE_ORDERED
 //The default behavior is to return an ordered array.
 $row = array (
     0 => <column "id" data>,
     1 => <column "name" data>,
     2 => <column "email" data>
 );
 
 $id = $row[0];
 
 //With $mode = DB_FETCHMODE_ASSOC
 //Returns an associative array with column names as array keys:
 $row = array (
     'id'    => <column "id" data>,
     'name'  => <column "name" data>,
     'email' => <column "email" data>
 );
 
 $id = $row['id'];
 
 //With $mode = DB_FETCHMODE_OBJECT
 //Returns a DB_row object with column names as properties:
 $row = db_row Object 
 (
     [id]    => <column "id" data>,
     [name]  => <column "name" data>,
     [email] => <column "email" data>
 )
 
 $id = $row->id;
 ?>
=============================
控制获取数据的数量 
<?php
 ...
 // the row to start fetching
 $from = 50;
 // how many results per page
 $res_per_page = 10;
 // the last row to fetch for this page
 $to = $from + $res_per_page;
 foreach (range($from, $to) as $rownum) {
     if (!$row = $res->fetchrow($fetchmode, $rownum)) {
         break;
     }
     $id = $row[0];
     ....
 }
 ?>
===========================
清楚结果释放变量
<?php
 ...
 $result = $db->query('SELECT * FROM clients');
 while ($row = $result->fetchRow()) {
     ...
 }
 $result->free();
 ?>
===========================