php毕业设计外文翻译--通过PHP访问MySQL

原文：Getting PHP to Talk to MySQlNow that you’re comfortable using the MySQL client tools to manipulate data in the database, you can begin using PHP to display and modify data from the database. PHP has standard functions for working with the databas e.First, we’re going to discuss PHP’s built-in database functions. We’ll also show you how to use the The PHP Extension and Application Repository (PEAR) databasefunctions that provide the ability to use the same functions to access any supported database. This type of flexibility comes from a process called abstraction. In programming interfaces, abstraction simplifies a complex interaction. It works by removing any nonessential parts of the interaction, allowing you to concentrate on the important pa rts. PEAR’s DB classes are one such database interface abstraction. The information you need to log into a database is reduced to the bare minimum. This standard format allows you to interact with MySQL, as well as other databases using the same functions. Similarly, other MySQL-specific functions are replaced with generic ones that know how to talk to many databases. For example, theMySQL-specific connect function is:mysql_connect($db_host, $db_username, $db_password);versus PEAR’s DB connect function:$connection =DB::connect("mysql://$db_username:$db_password@$db_host/$db_database");The same basic information is present in both commands, but the PEAR function also specifies the type of databases to which to connect. You can connect to MySQL or o ther supported databases. We’ll discuss both connection methods in detail.In this chapter, you’ll learn how to connect to a MySQL server fromPHP, how to use PHP to access and retrieve stored data, and how to correctly display information to the user.1 The ProcessThe basic steps of performing a query, whether using the mysql command-line tool or PHP, are the same:• Connect to the database.• Select the database to use.• Build a SELECT statement.• Perform the query.• Display the results.We’l l walk through each of these steps for both plain PHP and PEAR functions.2 ResourcesWhen connecting to a MySQL database, you will use two new resources. The first is the link identifier that holds all of the information necessary to connect to the database for an active connection. The other resource is the results resource. It contains all information required to retrieve results from an active database query’s result set. You’ll be creating and assigning both resources in this chapter.3 Querying the Database with PHP FunctionsIn this section, we introduce how to connect to a MySQL database with PHP. It’s quite simple, and we’ll begin shortly with examples, but we should talk briefly about what actually happens. When you try connecting to a MySQL database, the MySQL server authenticates you based on your username and password. PHP handles connecting to the database for you, and it allows you to start performing queries and gathering data immediately.As in Chapter 8, we’ll need the same pieces of information to connect to the database: • The IP address of the database server• The name of the database• The username• The passwordBefore moving on, make sure you can log into your database using the MySQL command-line client.4 Including Database Login DetailsYou’re going to create a file to hold the information for logging into MySQL. Storing this information in a file you include is recommended. If you change the database password, there is only one place that you need to change it, regardless of how many PHP files you have that access the database.You don’t have to worry about anyone directly viewing the file and getting your database login details. The file, if requested by itself, is processed as a PHP file and returns a blank page.5 Troubleshooting connection errorsOne error you may get is:Fatal error: Call to undefined functionmysql_connect( ) in C:\Program Files\ApacheSoftware Foundation\Apache2.2\htdocs\db_test.php on line 4This error occurs because PHP 5.x for Windows was downloaded, and MySQL support was not included by default. To fix this error, copy the php_mysql.dll file from the ext/ directory of the PHP ZIP file to C:\php, and then C:\WINDOWS\php.ini.Make sure there are two lines that are not commented out by a semicolon (;) at the beginning of the line like these:extension_dir = "c:/PHP/ext/"extension=php_mysql.dllThis will change the extension to include the directory to C:/php and include the MySQL extension, respectively. You can use the Search function of your text editorto check whether the lines are already there and just need to be uncommented, or whether they need to be added completely.You’ll need to restart Apache, and then MySQL support will be enabled.6 Selecting the DatabaseNow th at you’re connected, the next step is to select which database to use with the mysql_select_db command. It takes two parameters: the database name and,optionally, the database connection. If you don’t specify the database connection, the default is the connection from the last mysql_connect:// Select the database$db_select=mysql_select_db($db_database);if (!$db_select){die ("Could not select the database: <br />". mysql_error( ));}Again, it’s good practice to check for an error and display it every time you access the database.Now that you’ve got a good database connection, you’re ready to execute your SQL query.7 Building the SQL SELECT QueryBuilding a SQL query is as easy as setting a variable to the string that is your SQL query. Of co urse, 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.8 Executing the QueryTo 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: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 command-line client. To display them, you process each row, one at a time.9 Fetching and DisplayingUse 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:The columns of the result row are stored in the array and can be accessed one at a time. The variable $result_row accesses the second attribute (as defined in the query’s column order or the column order of the table if SELECT * is used) in the result row.10 Fetch typesThis is not the only way to fetch the results. Using mysql_fetch_array, PHP can place the results into an array in one step. It takes a result as its first parameter, and the way to bind the results as an optional second parameter. If MYSQL_ASSOC is specified, the results are indexed in an array based on their column names in the query. If MYSQL_NUM is specified, then the number starting at zero accesses the results. The default value, MYSQL_BOTH, returns a result array with both types. Themysql_fetch_assoc is an alternative to supplying the MYSQL_ASSOC argument.11 Closing the ConnectionAs a rule of thumb, you always want to close a connection to a database when you’redone using it. Closing a database with mysql_close will tell PHP and MySQL that you no longer will be using the connection, and will free any resources and memory allocated to it:mysql_close($connection)12 InstallingPEAR 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 4.3.0 or newer, it’s already installed. If you’rerunning PHP 5.0, PEAR has been split out into a separate package. The DBpackage 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.译文：通过PHP访问MySQL现在你已经可以熟练地使用MySQL客户端软件来操作数据库里的数据，我们也可以开始学习如何使用PHP来显示和修改数据库里的数据了。