【導讀】以開始學習如何使用PHP來顯示和修改數據庫里的數據了。PHP有標準的函數用。我們首先學習PHP內建的數據庫函數，然后會學習PHP擴展和應用程序庫（PEAR，這種靈活性源自于抽象。對于編程接口而言，它將交互過程中無關緊要的部分屏蔽起來，讓你關。注于重要的部分。據庫所需要提供的信息被減少到最少。這種標準的格式可以通過同一個函數來訪。問MySQL以及其他的數據庫。比如，MySQL特定的連接函數是：。我們會詳細討論這兩種。我們將逐一介紹如何用PHP和PEAR的函數完成上面的每一步。當連接到MySQL數據庫的時候，你會使用到兩個新的資源。第一個是連接的標識。符，它記錄了一個活動連接用來連接到數據庫所必需的所有信息。MySQL數據庫的時候，MySQL服務器會根據你的用戶名和密碼進行身份認證。在開始之前，首先使用MySQL的命令行客戶端確認你登錄到數據庫。SELECT語句發(fā)生在第三個函數調用之前，但是在圖中沒有顯示出來。何被直接請求，這個文件會被當作PHP文件處理，返回結果是一個空白頁。

　　

【正文】 uery is as easy as setting a variable to the string that is your SQL query. Of course, you’ll need to use a valid SQL query, or MySQL returns with an error when you execute the query. The variable name $query is used since the name reflects its purpose, but you can choose anything you’d like for a variable name. The SQL query in this example is SELECT * FROM books. Unlike when you used the mysql mandline client, the query does not have a semicolon at the end. You can build up your query in parts using the string concatenate (.) operator: // Assign the query $select = 39。 SELECT 39。 $column = 39。 * 39。 $from = 39。 FROM 39。 $tables = 39。 books 39。 $where = 39。 NATURAL JOIN authors39。 $query = $select.$column.$from.$tables.$where。 This code is a more flexible version of the following: // Assign the query $query = SELECT * FROM books NATURAL JOIN authors。 20 The query string could also use a variable in the WHERE clause to limit which rows are returned based on user information or another query. Now that you have your query assigned to a variable, you can execute it. Executing the Query To have the database execute the query, use the mysql_query function. It takes two parameters—the query and, optionally, the database link—and returns the result. Save a link to the results in a variable called, you guessed it, $result! This is also a good place to check the return code from mysql_query to make sure that there were no errors in the query string or the database connection by verifying that $result is not FALSE: // Execute the query $result = mysql_query( $query )。 if (!$result){ die (Could not query the database: br /. mysql_error( ))。 } When the database executes the query, all of the results forma result set. These results correspond to the rows that you saw upon doing a query using the mysql mandline client. To display them, you process each row, one at a time. Fetching and Displaying Use mysql_fetch_row to get the rows from the result set. Its syntax is: array mysql_fetch_row ( resource $result)。 It takes the result you stored in $result fromthe query as a parameter. It returns one row at a time from the query until there are no more rows, and then it returns FALSE. Therefore, you do a loop on the result of mysql_fetch_row and define some code to display each row: // Fetch and display the results while ($result_row = mysql_fetch_row(($result))){ echo 39。Title: 39。.$result_row[1] . 39。br /39。 echo 39。Author: 39。.$result_row[4] . 39。br / 39。 echo 39。Pages: 39。.$result_row[2] . 39。br /br /39。 } The columns of the result row are stored in the array and can be accessed one at a time. The variable $result_row[2] accesses the second attribute (as defined in the query’s column order or the column order of the table if SELECT * is used) in the result row. Fetch types This is not the only way to fetch the results. Using mysql_fetch_array, PHP can place the results into an array in one step. It takes a result as its first parameter, and the way to bind the results as an optional second parameter. If MYSQL_ASSOC is specified, the results are indexed in an array based on their column names in the query. If MYSQL_NUM is specified, then the number starting at zero accesses the results. The 21 default value, MYSQL_BOTH, returns a result array with both types. The mysql_fetch_ assoc is an alternative to supplying the MYSQL_ASSOC argument. If you rewrote the code shown previously to use mysql_fetch_array with an associative indexed array, it would look like this: // Fetch and display the results while ($result_row = mysql_fetch_array($result, MYSQL_ASSOC)){ echo 39。Title: 39。.$result_row[39。title39。] . 39。br /39。 echo 39。Author: 39。.$result_row[39。author39。] . 39。br / 39。 echo 39。Pages: 39。.$result_row[39。pages39。] . 39。br /br /39。 } Closing the Connection As a rule of thumb, you always want to close a connection to a database when you’redone using it. Closing a database with mysql_close will tell PHP and MySQL that you no longer will be using the connection, and will free any resources and memory allocated to it: mysql_close($connection) Using PEAR PEAR is a framework and distribution system for reusable PHP ponents, creating a collection of addon functionalities for PHP development. There are many modules available to handle everything fromsession management to shopping cart functionality. Categories of modules that are currently available are listed in Table 91. Table 91. PEAR modules categories Authentication HTML Processing Benchmarking HTTP Science Caching Images Semantic Web Configuration Internationalization Streams Console Logging Structures Database Mail System Date/Time Math Test Encryption Networking Tools and utilities Event Numbers Validate File formats Payment Web services File system PEAR XML GTK ponents PHP Our list is not plete. Visit to find out all of the modules thatare available for download. Installing PEAR uses a Package Manager that oversees which PEAR features you install. Whether you need to install the Package Manager depends on which version of PHP you installed. If you’re running PHP or newer, it’s already installed. If 22 you’rerunning PHP , PEAR has been split out into a separate package. The DB package that you’re interested in is optional but installed by default with the Package Manager. So if you have the Package Manager, you’re all set. Unix You can install the Package Manager on a Unix systemby executing the following from the shell (mandline) prompt: