Mysql your visual blueprint for creating open source databases- P13 ppt

■ The System variables and their values are displayed. ˇ Click the Home link to return to the main phpMyAdmin page. Á Click the Show processes link. ■ The MySQL server's current process list is displayed. ‡ Click the Home link to return to the main phpMyAdmin page. When you select the Users option, the user table in the mysql database is opened, and the list of current users is displayed. The Edit link next to each username allows you to change the user's hostname and assign privileges. The Delete link deletes a user. The Grants link displays the current list of privileges granted to a user, and allows you to delete or modify the privileges. The Users page also includes a form that allows you to create a new user. You can specify the hostname the user is allowed to connect from, a password, and the privileges the user should be assigned for a particular database. You can also open the mysql database directly in phpMyAdmin to work with the various security tables. Keep in mind that this feature is potentially dangerous; if you mistakenly delete the root user, for example, you can lose access to the server. See Chapter 11 for more information about managing MySQL security. For details on using phpMyAdmin to manage a MySQL server, see the official documentation. The complete phpMyAdmin documentation is usually installed when you set up this utility. To access your local copy of the documentation, follow the phpMyAdmin documentation link on the main page. 227 USING MYSQL WITH PHP 12 516922 Ch12.F 9/26/02 11:40 AM Page 227 ⁄ Type <?php to start the PHP script. Note: You will usually want to include basic HTML tags, as shown here. ¤ Type mysql_connect( to begin the command. B efore you can use any MySQL functions in PHP, you must first open a connection to the MySQL server. You can do this using the mysql_connect function. To use this function, specify a hostname, username, and password for the MySQL server: $link=mysql_connect("localhost", "testuser", "testpw"); This command opens a connection to the MySQL server and returns a link identifier that can be used to perform operations on the server. In this example, the identifier is stored in the $link variable. If the connection to the server is not opened successfully, the boolean value false is returned, and an error message is displayed. If you do not specify one or more of the parameters for the mysql_connect command, PHP assumes default values. It attempts to use localhost as the server hostname, the username the Web server uses for PHP, and no password. If these values do not work on your MySQL server, an error will be returned unless you specify a valid hostname, username, and password. After you have opened a connection to the MySQL server, you can use the connection throughout the PHP script. If you only have a single connection to a single server open, you can use it without needing the link identifier. The connection to the MySQL server stays open until your PHP script ends, or until you explicitly close the connection. To close a connection, use the mysql_close command and specify the link identifier returned when you opened the connection. This command closes the link opened by the previous example: mysql_close($link); CONNECT TO A MYSQL SERVER MySQL 228 CONNECT TO A MYSQL SERVER 516922 Ch12.F 9/26/02 11:40 AM Page 228 ‹ Add the hostname, username, and password for your MySQL server. Note: See Chapter 11 for information on creating a username and password. › If desired, add a variable to store the link identifier returned by mysql_connect. ˇ End the command with a closing parenthesis and a semicolon, and press Enter. Á Type ?> to end the script. Note: Add any commands to work with the server before this tag. ■ This completes the PHP script to connect to MySQL. MySQL also supports persistent connections. This is a special type of connection that stays open even after the PHP script ends. If the same user attempts to connect to the server a second time, PHP finds the existing connection and returns its identifier rather than returning a new connection. To use persistent connections, use mysql_pconnect() to open the connection. The arguments for this function are the same as for the standard mysql_connect()function. You cannot close a persistent connection manually; instead, the server will keep the connection open until MySQL's wait_timeout period expires. See Chapter 10 for information on setting this timeout value on a MySQL server. Example: $link=mysql_pconnect("localhost", "testuser", "testpw"); // Add statements that use the database server here Persistent connections can be more efficient in an application where the same user will make many queries on different PHP scripts. In a simple application, they are less efficient because connections are left open and not used further, and MySQL may run out of connections for future clients. Persistent connections only work if PHP is running as a module on an Apache Web server. They are not currently supported when PHP is run as a CGI program or on other Web servers. 229 USING MYSQL WITH PHP 12 516922 Ch12.F 9/26/02 11:40 AM Page 229 Note: Start with a basic HTML document. ⁄ Type <?php and ?> to begin and end the PHP script. ¤ Type mysql_connect to begin the statement that connects to the database, and add the details for the server, username, and password. ‹ Type mysql_select_db followed by the database name to select the database for future queries. › Type mysql_query to begin the function that sends the query to the MySQL server, and add the query and a variable to store the result identifier. A fter you have connected to the MySQL server from a PHP script, you can run one or more MySQL queries. Often, you will want to send a SELECT query to the server and display the resulting data. PHP includes a number of ways to receive data from the SQL server. As with the MySQL monitor, before you can make a query, you must select a database. To do this, use the mysql_ select_db function. To use this function, specify the database name as a string: mysql_select_db("testdb"); After you have selected a database, you can send an SQL query to the server using the mysql_query function. To use this function, specify the query as a string. The following example sends a simple SELECT query to the server: $result=mysql_query("SELECT quote, author FROM quotes"); If the query is successful, the mysql_query function returns a result identifier. In this example, the $result variable stores the result identifier. You can use this identifier later in the script to display the query results. While the result identifier indicates that the query was successful, this only means that MySQL understood the query — it does not mean there are definitely one or more rows of data in the result. If the query is unsuccessful, the mysql_query function returns a FALSE value instead. Some queries, such as INSERT and DELETE, do not return data from the server. In this case, mysql_query simply returns TRUE if the query was successful. To display query results, you can use the mysql_fetch_row function. This function accepts a result identifier, and returns the next row of the result as an array. The array includes all of the columns of the result in order. You can repeat the function to retrieve all of the result rows. The following example uses a while loop to retrieve all of the rows: while(list($quote, $author) = mysql_fetch_row($result)) { echo "<p>$quote $author</p>"; } This example retrieves each row into the $quote and $author variables. These are used with an echo statement to display each row as an HTML paragraph. The list function allows the array returned by mysql_fetch_row to be stored in two regular variables instead of an array, and is a convenient way to handle simple queries. DISPLAY QUERY RESULTS MySQL 230 DISPLAY QUERY RESULTS 516922 Ch12.F 9/26/02 11:40 AM Page 230 ˇ Type while to begin the loop, and add the mysql_fetch_row statement. Include braces to enclose the loop. Á Type echo to begin the statement that displays each row. Add the string to display and a closing bracket to end the loop. ‡ Load your PHP document into a Web browser. ■ The rows of data are displayed within the HTML document. Note: This example uses the quotes table in the testdb database. You can import this table from the CD-ROM. USING MYSQL WITH PHP You can optionally specify a link identifier from mysql_connect as a second parameter to the mysql_select_db and mysql_query functions. However, these and most other MySQL functions in PHP default to using the last connection you opened, so this is usually not necessary. You can use the mysql_db_query function to avoid selecting a database first. This function is similar to mysql_query, but accepts a database name as its first parameter. To use this script or any PHP script you create, you must first save the edited file, and then upload it to your Web server that supports PHP. If you are using PHP version 3, save the file with the .php3 extension. For PHP version 4, save the file with the .php extension. After the file is saved, you will need to upload it to the correct directory of the Web server. You can do this using the same program you use to upload HTML documents. Typically this is done using the FTP protocol. After the file is uploaded to the server, you can use a Web browser to display the result. PHP does not require a particular browser because it creates HTML output. PHP pages display just like HTML pages. 231 12 516922 Ch12.F 9/26/02 11:40 AM Page 231 Note: Start with a basic HTML document. ⁄ Type <?php and ?> to begin and end the PHP script. ¤ Type mysql_connect followed by the correct user, password, and hostname to connect to the database. ‹ Type mysql_select_db followed by the database name to select the database for future queries. › Type $result = mysql_query to begin the function that sends the query to the MySQL server, and add the query in quotation marks. Note: This example uses the quotes table in the testdb database. You can import this table from the CD-ROM. W hen you use the mysql_fetch_row function to retrieve rows from a query, you must specify the column names in the query and retrieve them in the same order. If you are trying to use a query that returns all columns of a table, and are unsure of the order the columns will be returned in, you can use mysql_fetch_ object instead. For example, suppose you have made the following query to the MySQL server. This query retrieves all columns and all rows from the quotes table. $result=mysql_query("SELECT * FROM quotes"); To retrieve the data, you can use mysql_fetch_object. This returns an object whose properties are the column values for the row. Thus, you can refer directly to the MySQL column names rather than assigning your own variable names to each column. The following while loop uses the mysql_fetch_object function to retrieve and display each row: while($row = mysql_fetch_object($result)) { echo "<p>$row->quote $row->author</p>"; } In this example, the $row variable stores each row. You can use the -> operator to refer to each MySQL column name as a property of the object. Thus, you can refer to the quote column as $row->quote and the author column as $row- >author. Because the MySQL query specified the wildcard * rather than specific column names, all columns of the table are available from the object. You can use whichever function you are most comfortable with to return data from a MySQL query. The data returned is the same; only the method you use to access it changes. PHP includes several other fetch commands that return the results in different formats, such as mysql_fetch_assoc to store the data in an associative array. This type of array uses column names to index the results rather than numeric indexes. STORE QUERY RESULTS AS OBJECTS MySQL 232 STORE QUERY RESULTS AS OBJECTS 516922 Ch12.F 9/26/02 11:40 AM Page 232 ˇ Type while to begin the loop that iterates through the rows of data. Add the statement to retrieve a row and an opening brace to begin the loop. Á Type echo followed by a string using the $row object to display the row. Add the closing brace to end the loop. ‡ Load your PHP document into a Web browser. ■ The rows of data are displayed within the HTML document. If you are running into MySQL errors while attempting to use a database from PHP, it is useful to display the results within your PHP script. The following PHP script adds if statements to check whether each MySQL command succeeded. It displays an appropriate error message if any command fails. Example: <?php $link = mysql_connect("localhost", "testuser", "testpw"); if (!$link) echo "Failed to connect to MySQL server!"; $status=mysql_select_db("testdb"); if (!$status) echo "Failed to select database!"; $result=mysql_query("SELECT * FROM quotes"); if (!$result) echo "The MySQL query failed!"; while($row = mysql_fetch_object($result)) { echo "<p>$row->quote $row->author</p>"; } ?> This example checks the results of the mysql_connect, mysql_select_db, mysql_query, and mysql_fetch_object commands. All of these return a FALSE value if they fail. The one condition that these do not account for is if the query succeeds but returns a zero-row result. If this happens, the while loop will end immediately without displaying any data. 233 USING MYSQL WITH PHP 12 516922 Ch12.F 9/26/02 11:40 AM Page 233 Note: Start with a basic HTML document. ⁄ Type <?php and ?> to begin and end the PHP script. ¤ Type mysql_connect followed by the username, host, and password to connect to the MySQL server. ‹ Type mysql_select_db followed by the database name to select the database. Note: This example uses the testdb database and the scores table. You can import this table from the CD-ROM. › Type $query= followed by the MySQL query in quotation marks. ˇ Type $success = mysql_query ($query); to create the statement that sends the query to the server. Y ou can use the mysql_query command in PHP to send an INSERT query to the MySQL server. When you do this, a result identifier is not returned because an INSERT query does not return any data from the MySQL server. Instead, the result returned from mysql_query is a simple true or false value that indicates whether the query was successful. For example, the following PHP statements add a record to the scores table and display a message indicating success or failure: $query="INSERT INTO scores (name, score) VALUES ('Fred', 92)"; $success = mysql_query($query); if ($success) echo "The INSERT query was successful."; else echo "Error: INSERT query failed."; This example stores the query in the $query variable, and then uses the mysql_query function to send the query to the MySQL server. The result of the query is stored in the $success variable. The if statement checks this variable and displays a success message, and the else statement displays an error message if the insert was unsuccessful. Unlike SELECT queries, an INSERT query does not return a result identifier. The result stored in the $success variable will be a simple TRUE or FALSE value. As with other MySQL queries, you must first connect to the MySQL server using the mysql_connect function, and then select a database with mysql_select_db before attempting to insert a row. You must be connected using a MySQL username that has the INSERT privilege for the table you are using in the INSERT command. Because double quotation marks are used to define the $query string, you cannot use double quotes inside the query. You can substitute single quotation marks within the query. Only values to be stored in text columns need to be quoted. You can use a PHP variable within the INSERT query by including its name in the $query string. INSERT A RECORD FROM PHP MySQL 234 INSERT A RECORD FROM PHP 516922 Ch12.F 9/26/02 11:40 AM Page 234 Á Type if to begin the statement that checks whether the query succeeded, followed by echo and the success message in quotation marks. ‡ Type else to begin the statement that checks for an error, and type echo followed by the error message. ° Load the PHP document into a Web browser. ■ The displayed message indicates whether the INSERT query was successful. If a table includes an auto-increment column, it will automatically be updated with a new unique value each time you insert a record. After you have inserted a row into a table from PHP, you can use the mysql_insert_id function to find out what number was assigned to the auto-increment field in the INSERT query. This technique is useful because you now have a value that you can use to find the inserted row in a subsequent query. Without this feature, you would have to use a separate query to find the newest row, and even that may find a row inserted by a different user. For example, the following PHP code inserts a row into the quotes table and then displays the ID assigned to the auto-increment field. Example: $link=mysql_connect("localhost", "testuser", "testpw"); mysql_select_db("testdb"); $query = "INSERT INTO quotes (quote, author) VALUES "; $query .= "('Union gives strength.', 'Aesop')"; $success = mysql_query($query); if ($success) { echo "The INSERT query was successful."; echo "The record number is: " + mysql_insert_id(); } else echo "Error: INSERT query failed."; You can optionally specify a link identifier from mysql_connect with the mysql_insert_id function. If you do not use an identifier, the most recent connection used is assumed. 235 USING MYSQL WITH PHP 12 516922 Ch12.F 9/26/02 11:40 AM Page 235 Note: Start with a basic HTML document. Note: This example uses the scores table in the testdb database. ⁄ Type <?php and ?> to begin and end the PHP script. ¤ Type mysql_connect followed by the username, password, and hostname to connect to the MySQL server. ‹ Type mysql_select_db followed by the database name to select the database. › Type $query= followed by the DELETE query. ˇ Type $success=mysql_ query($query); to send the query to the server. Y ou can also use PHP to send a DELETE query to the MySQL server. As with an INSERT query, when you use the mysql_query function with a DELETE query, a simple true or false result is returned that indicates whether the delete was successful. To delete one or more rows of a table, you usually will need to specify a WHERE clause. Without this clause, all records of the table would be deleted. The following PHP statements send a DELETE query to the MySQL server: $query="DELETE FROM scores WHERE name = 'fred'"; $success=mysql_query($query); if ($success) echo "The DELETE query was successful."; else echo "Error: DELETE query failed."; These statements store the query in the $query variable and send it to the MySQL server using the mysql_query function. The if statement displays a message if the DELETE query succeeded, and the else statement displays a message if the query failed. Note that a failed query is not the same as a nonmatching WHERE clause. If the WHERE clause does not match any records, the mysql_query function will still succeed. The query will only fail if the server cannot be reached, or if there is a syntax error in the query. You can find out how many rows were affected by the DELETE query with the mysql_affected_rows function. This function returns the number of rows affected by the most recent DELETE, INSERT, or UPDATE query. You can use this to determine how many rows the WHERE clause matched. DELETE RECORDS USING PHP MySQL 236 DELETE RECORDS USING PHP 516922 Ch12.F 9/26/02 11:40 AM Page 236 [...]... password, and hostname to connect to the MySQL server Á Type mysql_ select_db followed by the database name to select the database 516922 Ch12.F 9/26/02 11:40 AM Page 239 USING MYSQL WITH PHP 12 The form in this example uses the HTML tag to begin a form Within the and tags, you can use various HTML tags to define form elements for different input types This example uses two different... handle the form results PHP automatically stores the form values as variables In this case, the $quote and $author variables store the entered data You can make these variables part of an INSERT query and send it to the MySQL server with the mysql_ query function The following PHP code adds a record from the form: The tag in HTML starts an HTML form You can use the action attribute of the tag... This code creates a SELECT query, placing the $search value from the form into a WHERE clause It then uses mysql_ query to submit the query to MySQL, and a while loop with the mysql_ fetch_object function to display the results CREATE A DATABASE SEARCH FORM Note: Start with a basic HTML document ⁄ Type and to define the HTML form ‹ Type to begin and end the PHP script Note: This... AM Page 238 MySQL CREATE A FORM TO ADD RECORDS ne of the strengths of PHP is its ability to work directly in an HTML document You can create an HTML form and use a PHP script in the same document to write the data entered into the form to a MySQL database As an example, you can create an HTML form and PHP script that allow you to add a row to the quotes table O After you have defined the form, you can... runs a SELECT query using the value entered into the form and displays the results As an example, you can create a form to search the quotes table The following HTML tags define the form: Search for: This defines a form that sends data to search.php, the filename of the... ⁄ Type and to define the HTML form ‹ Type to begin and end the PHP script Note: This example uses the quotes table in the testdb database ¤ Type to define the form fields › Type if ($add) to begin a statement that checks whether the form has already been submitted 238 ˇ Type mysql_ connect followed by the username, password, and hostname to connect to the MySQL server... and click into a Web browser the Submit button s The HTML form is s The form is displayed displayed again, and a message indicates that the INSERT query was successful 239 516922 Ch12.F 9/26/02 11:40 AM Page 240 MySQL CREATE A DATABASE SEARCH FORM A nother common application of PHP is to create a search engine for a database You can use an HTML form and a short PHP script to search a table The PHP script... program that handles the results of the form In the case of PHP, you can specify the same file that contains the form itself The following HTML defines a form that calls the add.php script: if ($add) { mysql_ connect("localhost", "testuser", "testpw"); mysql_ select_db("testdb"); $query="INSERT INTO quotes(quote, author)"; $query.=" VALUES( '$quote','$author')"; $result =mysql_ query($query); if ($result) echo... script can check for the submit button, and if it has been clicked, display the results of a search The following section of PHP handles the search: if ($submit) { echo "Searching for: $search"; mysql_ connect("localhost", "testuser", "testpw"); mysql_ select_db("testdb"); $query="SELECT * FROM quotes WHERE quote LIKE '%$search%' "; $result =mysql_ query($query); while ($row = mysql_ fetch_object($result))... PHP script The if statement within the PHP script checks for the $add variable to see whether the form has already been submitted ‡ Type $query= followed by the beginning of the MySQL query · Type $result =mysql_ query($query); to send the query to the MySQL server ° Type $query.= followed by ‚ Type if ($result) to check the conclusion of the MySQL query the result, and type echo followed by a message . SERVER MySQL 228 CONNECT TO A MYSQL SERVER 516922 Ch12.F 9/26/02 11:40 AM Page 228 ‹ Add the hostname, username, and password for your MySQL server. Note: See Chapter 11 for information on creating. here. ¤ Type mysql_ connect( to begin the command. B efore you can use any MySQL functions in PHP, you must first open a connection to the MySQL server. You can do this using the mysql_ connect. will keep the connection open until MySQL& apos;s wait_timeout period expires. See Chapter 10 for information on setting this timeout value on a MySQL server. Example: $link =mysql_ pconnect("localhost",