F27DB Introduction to Database Systems
Accessing MySQL database via PHP - 2
Helen Hastie
hhastie@hw.ac.uk
Room: EM2.44
Material available on Vision (modified from slides by Monica Farrow)
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Intro PHP & MySQL
1
Recap
•Website design
Login
Covered in
lecture 5
Request spy details
(Enter code)
Spy details
displayed
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Choices
Enter new spy
(enter details)
Add
confirmed
Intro PHP & MySQL
Update spy
(enter details)
Changes
confirmed
2
Recap - sessions
• Sessions are visits to a website
• PHP provides functions for managing sessions
• Use session_start() before outputting any html
• Session variables are used to store and
retrieve session data
• E.g. Adding a session variable
$_SESSION[‘password’]=$_POST[‘password’];
• E.g. Retrieving a session variable
$password = $_SESSION[‘password’];
• A session ends when the user moves away
from the site, or it can time-out
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Recap - Display spy - response
• Links to other actions
• One table for the Spy data
• Another for the skills
• To keep things simple,
I am using the column
name from the database
as headings
• Not ideal!
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Recap : dbfunctions.php file
• This file contains my own functions to run
each of the mysql database functions, and also
to automatically display a table
• This makes the code in the main script easier to
read
• Instead of lots of blocks of code ‘do this, then see if it
works’ one after the other, you see simpler code, shown on
the next slide
• It means that beginning programmers can use my
example php scripts, and only change
• Their username
• the SQL queries
• the parameters from the form, which are needed for the
SQL query
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Creating the form to add a spy
• Mostly html here
• heading
• Links
• Input fields
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Error prevention
• For gender, use radio
buttons to ensure that
only valid options are
entered
• Use php scripts to get
values from MySQL for
drop-down list and the
multiple option box
• The php scripts query the
database to find out the
existing spymasters and
skills
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Creating the SpyMaster option list
• Retrieve username and password from session
variables
• Connect to database
• Run query to find all spymaster codenames
• 'SELECT mCodeName FROM SpyMaster';
• Create html option list from that
//find all the spymaster codenames
$query = 'SELECT mCodeName FROM SpyMaster';
$result = runQuery($query);
//now need to display in option box - pto
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Display spymaster options
//PUT EACH SPYMASTER CODENAME INTO AN OPTION BOX
//first print out blank initial option
print '<select> <option value = ""> </option>';
//get each row in turn
while ($row = mysql_fetch_row($result) )
{
//get value of first (only) column in the row
//and place as value and display in option
print '<option value="' . $row[0 ]. '">'
. $row[0] . '</option>';
}
print '</select>';
}
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Display skill options
•
•
•
•
Very similar to the spymaster code
The skill name is value displayed for the user to choose
The skill code is the value to be sent to the next script
A multiple option box is created which returns all
selected items in an array
//option value is code, but name is displayed
$query = "SELECT skillCode, skillName FROM SpySkillList";
$result = runQuery($query);
print '<select name = "skill[]" multiple>';
while ($row = mysql_fetch_row($result) )
{
print '<option value="' . $row[0 ] . '">' .
$row[1] . '</option>';
}
print '</select>';
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Receiving the data
• The script referred to in the form’s action
attribute, which generates the response,
must:
•
•
•
•
Start a session & retrieve username and password
Output initial html
Pick up all the form parameters
Create an INSERT command with all the
parameters
• Run it
• Report whether it worked or not
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Creating the insert command
• Picking up the form parameters
• Creating the INSERT command
• Notice outer double quotes, inner single quotes
• It’s probably a good idea to test this out at this
stage, just printing the insert command to make sure
it looks alright, before trying to run it
//First pick up the parameters
//from the form
$spycode = $_POST["codename"];
$firstName = $_POST["first"];
Etc etc
//define and run the insertion
$query = "INSERT INTO Spy VALUES
('$spycode', '$firstName', '$lastName',
'$date', '$gender', '$mark', 0, '$spymaster', NULL )";
print $query . "<br/>"; /
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Inserting the spy
• Run it using the function mysql_query and
test to see whether it worked
• Print whether the insertion was a success or
not. Exit if not.
$insResult = mysql_query($query);
if ($insResult)
print("Spy details for " . $firstName . " "
. $lastName . " have been inserted<br/>");
else
//vital to know why it failed
exit ( $query. " " . mysql_error().
"</p></body></html>");
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Inserting the skills
• A new record must also be created in the
SpyWithSkill table, for each skill in the skill
array parameter
• Consists of the spy code and the skill code
$skills = $_POST['skill'];
foreach($skills as $skill) //for each skill
{
$query = "INSERT INTO SpyWithSkill
VALUES ('$spycode', $skill)";
print $query . '<br/>';
$insResult = mysql_query($query);
if ($insResult)
{
print("Spy skill inserted<br/>");
}
else
exit ( mysql_error(). "</p></body></html>" );
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Problems with insertions
• What sort of things can go wrong with
insertions?
• Duplicate Primary Key
• A record already exists with this primary key
• Foreign key invalid
• No matching value exists in the referenced table
• Invalid data
• Incorrect range, incorrect data type, incorrect length
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Insertion error prevention / feedback
• Today’s example just prints out the mysql
error message, which wouldn’t be very friendly
for a user
• It would be better to determine what is wrong and
output a suitable message for the user
• Frequently javascript is used in the HTML
form to ensure that the data is acceptable
• Not covered in this module
• It may be that the user’s computer has javascript
disabled or otherwise not functioning
• So ideally all these values should be checked in the PHP
script too
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Running an update command
• Updates work exactly like insertions
• Gather the data via a form and post to a php script
• Create an UPDATE command in PHP, using
parameter data
• Run the Update command
• Check that it worked and output feedback
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Dates
• To insert a date to MySQL, we need it in the
format YYYY-MM-DD
• E.g INSERT INTO MyTable
VALUES ( …, …, …, ‘2008-12-04’,…,…);
• To insert today’s date, you can use the
MySQL CURDATE() function:
• E.g. INSERT INTO MyTable
VALUES ( …, …, …, CURDATE(),…,…);
• You can also use CURRENT_DATE() which is a
synonym for CURDATE()
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PHP, objects and extensions
• PHP can be used in a ‘procedural’ way, as here
• work your way through the lines of code, use
functions to reduce code duplication and simplify
the main script
• However recent versions also allow objectoriented programming and exception handling
• Not covered in this module
• You may see examples of this on the web or in
books
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Beyond MySQL and PHP
• A brief look at wider issues
• Dynamic and static web pages
• Connecting to a database from a programming
application
• Programming and SQL
• Interoperability
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Static and dynamic web pages
• Some web pages are static
• The html never changes. These pages can be
written entirely in html.
• Examples are the Request Spy Details page, &
initial Log-in page
• Many web pages are dynamic
• Some of the html never changes
• Some is determined at run-time, and depends on
the request. This usually involves the submission of
data from html forms, and connection to a
database to query or update records
• Suitable software includes PHP & MySQL
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Querying and updating a database
• The process is the same for all databases and
server-side languages
• Submit a request, probably with data in parameters
• Using a script or programming language
•
•
•
•
•
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Connect to the database
create SQL command including this data
Submit the command to the database
Process the result obtained from the database
Output the response, consisting of appropriate html,
which may contain data from the database
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Connecting to the database
• There are different databases and different
scripting languages
• How to know how to connect?
• The ODBC standard, pioneered by Microsoft, is an
Open Database Connectivity standard
• Aims to be independent of database, programming language or
operating system
• There are ODBC drivers for most DBMS
• It may be necessary to locate/install these
• ODBC forms the basis of other connectivity such as
JDBC (java connectivity) and OLE-DB (later Microsoft
version)
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ODBC Architecture : 4 levels
• The application uses a driver to submit
SQL statements and retrieve results.
• The driver manager helps the
application find a driver.
• The driver translates the application's
data queries into commands that the
DBMS understands. Both the
application and the DBMS must be
ODBC-compliant -- that is, the
application must be capable of issuing
ODBC commands and the DBMS must
be capable of responding to them
• A data source is a collection of data
(usually a database) which the driver
can query.
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Application
Driver Manager
Driver
Driver
Driver
Data
Data
Data
Source Source Source
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SQL and programming
• SQL alone is insufficient for an application
• Need some type of programming language to deal
with logic (alternatives, repetition)
• Some DBMS have included programming
functionality as an extension of SQL
• An example is Oracle’s PL/SQL
• Includes loops and conditional statements
• Procedures, functions and triggers can be created
and stored within the database
• A good solution for SQL intensive applications
• For applications which are logic-intensive,
SQL can be included within a programming
language - pto
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Programming SQL
• A database can be accessed from a
programming language in one of two ways:
• Embedded SQL
(not covered)
• directly embedding SQL statements in the program
source.
• A precompiler is required to replace SQL
statements with calls to DBMS routines.
• A Database Connectivity API, like ODBC or
JDBC (how PHP accesses MySQL)
• a standard set of functions in the language that
access the database, using hidden 'compiler magic'.
• Avoids the need for precompilation and is more
portable – but involves more use of Strings
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Interoperability?
• Relational systems with SQL provide a single model
for data and so should provide good support for such
general application development (one application, easy
to alter the database)
• But:
•
•
•
•
•
•
the programming interface to SQL varies
the functionality provided varies
the flavour of SQL varies
the system catalog varies - e.g. domain names
some data is not in a database
DBMS vendors pride themselves on adding extra functionality
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The MySpy website
• My Spies website is available for downloading
on the module website
• Download it, put into your www folder, and play
with it using a URL like
http://www2.macs.hw.ac.uk/~username/IntroDB/S
pies/SpyStart.html
• You can then take another copy and adapt it for
use in your coursework, rather than starting from
scratch, although you can also do this if you prefer!
• NOW INCLUDES Insert example page too
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