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PHP and MySQL
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PHP and MySQL
Topics
 Querying Data with PHP
 User-Driven Querying
 Writing Data with PHP and MySQL
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PHP and MySQL
Querying Data with PHP
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Opening and Using a Database
Error Handling of MySQL Database Functions
Formatting Results
Using Include Files
PHP and MySQL
Opening and Using a Database
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In PHP, there is no consolidated interface.
A set of library functions are provided for
executing SQL statements, as well as for
managing result sets returned from queries,
error handling, and setting efficiency options.
Connecting to and querying a MySQL DBMS
with PHP is a five-step process:
1. Connect to the DBMS and use a database.
» Open a connection to the MySQL DBMS using
mysql_connect( ).
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PHP and MySQL
Opening and Using a Database
» There are three parameters:
The hostname of the DBMS server to use
 A username
 A password
» Once you connect, you can select a database to use
through the connection with the mysql_select_db( )
function.
» The function mysql_connect( ) returns a connection
handle.
» A handle is a value that can be used to access the
information associated with the connection.
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PHP and MySQL
Opening and Using a Database
2. Run the query using mysql_query( ).
» The function takes two parameters:
 The SQL query itself
 The DBMS connection to use
 The connection parameter is the value returned
from the connection in the first step.
» The function mysql_query( ) returns a result set
handle resource; that is, a value that can retrieve the
output—the result set—of the query in Step 3.
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PHP and MySQL
Opening and Using a Database
3. Retrieve a row of results.
» The function mysql_fetch_row( ) retrieves one row of
the result set.
» The function takes only one parameter:
 The result set handle from the second step
» Each row is stored in an array $row, and the attribute
values in the array are extracted in Step 4.
» A while loop is used to retrieve rows until there are
no more rows to fetch.
» The function mysql_fetch_row( ) returns false when
no more data is available.
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PHP and MySQL
Opening and Using a Database
4. Process the attribute values.
» For each retrieved row, a for loop is used to print
with an echo statement each of the attributes in the
current row.
» Use mysql_num_fields( ) is used to return the
number of attributes in the row; that is, the number
of elements in the array.
» The function takes only one parameter:
 The result set handle from the second step
» The data itself is stored as elements of the array
$row returned in Step 3.
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PHP and MySQL
Opening and Using a Database
5. Close the DBMS connection using mysql_close( )
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The function takes only one parameter:
 The connection to be closed.
Example 4-1
Example 4-2
Example 4-3
Example 4-4
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PHP and MySQL
Error Handling of MySQL Database Functions
 Database functions can fail.
 There are several possible classes of failure,
ranging from critical—the DBMS is inaccessible
or a fixed parameter is incorrect to recoverable,
such as a password being entered incorrectly by
the user.
Example 4-5
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PHP and MySQL
Formatting Results
 Basic techniques for connecting to and querying
a MySQL DBMS using PHP can be extended to
produce results with embedded HTML that have
both better structure and presentation.
Example 4-6
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PHP and MySQL
Using Include Files
 Include directives allow common functions in
other files to be accessible from within the body
of a script without directly adding the functions to
the code.
Example 4-7
Example 4-8
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PHP and MySQL
User-Driven Querying
 User Input
 Passing Data with URLs
 Passing Data with the HTML <form> Environment
 Passing Data with Embedded Links
 How PHP Initializes Variables
 Querying with User Input
 Combined Scripts
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PHP and MySQL
User Input
 Three techniques can be used to pass data that
drives the querying process in a web database
application:
 Manual entry of a URL to retrieve a PHP script
resource and provide parameters to the resource.
» For example, a user may open a URL using the Open Page
option in the File menu of the Netscape web browser.
 Data entry through HTML <form> environments.
» For example, <form> environments can capture textual
input, and input is made by selecting radio buttons, selecting
one or more items from a drop-down select list, clicking on
buttons, and through other data entry widgets.
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PHP and MySQL
User Input
 Embedded hypertext links that can be clicked to
retrieve a PHP script resource and provide
parameters to the script.
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PHP and MySQL
Passing Data with URLs
 Before the script is processed by the PHP
scripting engine, variables associated with any
parameters to the resource are initialized and
assigned values.
Example 5-1
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PHP and MySQL
Passing Data with the HTML <form> Environment
 The second technique that captures data passed
from a browser to a server is the HTML <form>
environment.
Example 5-2
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PHP and MySQL
Passing Data with Embedded Links
 The third technique that passes data from a web
browser to a web server is embedding links in an
HTML document.
 This technique runs queries in most web
database applications and is conceptually similar
to manually entering a URL.
Example 5-3
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PHP and MySQL
How PHP Initializes Variables
 When the PHP script engine is invoked, the
engine declares and initializes variables in a
predefined order.
 The automatic initialization feature works in this
order:
1. By default, environment variables are initialized
first.
2. Variables are initialized from query string
parameters passed with the GET method.
3. POST method parameters are initialized.
4. Variables from cookies are initialized.
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PHP and MySQL
How PHP Initializes Variables
5. The Apache server internal variables are
initialized.
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The initialization order can be changed from
the default by adjusting the variables_order
setting in php.ini.
PHP and MySQL
Querying with User Input
 To introduce querying with user input, we begin
by explaining a script that retrieves the wines
made in a wine region that is specified by a user.
Example 5-5.
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PHP and MySQL
Combined Scripts
 Some approaches separates the HTML <form>
and the PHP processing script into two files.
 It is more common to implement both in the
same script where the code can produce a
<form> or run a query, depending if user
parameters are supplied.
 If the script is called with no parameters, the
script produces a <form> for user input and, if it
is called with input from the <form>, it runs the
query. This is called a combined script.
Example 5-6.
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PHP and MySQL
Writing Data with PHP and MySQL
 Database Inserts, Updates, and Deletes
 Uploading and Inserting Files into Databases
 Updating data
 Deleting data
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PHP and MySQL
Database Inserts, Updates, and Deletes
 Simple database insertions and updates are
much the same as queries.
 Inserting, updating, and deleting data does
require some additional care.
Example 6-1
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PHP and MySQL
Inserting data
 Phase one of the insertion process is data entry.
Example 6-5
 The second phase of insertion is data validation
and then the database operation itself.
Example 6-6
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PHP and MySQL
Updating data
 Updating data is usually a more complex
process than inserting it. A three-step process
for updates is used in most web database
applications:
 Using a key value, matching data is read from the
database.
 The data is presented to the user for modification.
 The data is updated by writing the modified data
to the database, using the key value from the first
step.
Example 6-7
Example 6-8
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PHP and MySQL
Deleting data
 The basic principle of deletion is a two-step
process:
 Identify the row or rows to be deleted
 Remove the data with an SQL DELETE
statement.
 As in an update, the first step requires a key
value be provided, and any technique described
for capturing keys in updates can be used.
 We assume here that a unique, primary key
value for the row to be deleted is available.
Example 6-8-1
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