PHP and Mysql

PHP-MySQL database
applications

PHP-MySQL database applications
Brief review of MySQL
PHP MySQL functions
examples

Brief Review Of MySQL
The MySQL comand line monitor
Creating database tables
Queries

Command Line Client
Read the MySQL documentation
c:mysqlmysqldocsmanual_toc.html

Read MySQL install instructions on CDSupply a
username
Command to enter monitor is
and a
mysql - u xxxx -p

To execute an SQL script use

password
when
prompted

mysql -u xxxx -p < /path/script.sql

GUI client MyCC is better

Creating Database Tables
Create web_db database to hold the tables:
CREATE DATABASE web_db;

To create a table called notes:
USE web_db;
CREATE TABLE notes (...);
insert some rows for testing if necessary

It is easy to write an sql script called
notes.sql and use monitor to execute it

The Basic Queries
CREATE

create databases and tables

SELECT

select table rows based on certain conditions

DELETE

delete one or more rows of a table

INSERT

insert a new row in a table

UPDATE

update rows in a table

ALTER

alter the structure of a table

PHP MySQL Functions
Connecting to a Database
Making a query
Using results of a query
freeing resources
closing the connection

Connecting To A Database
mysql_connect(server, username, password)
connects to a MySQL server through a port
the default is the string "localhost:3306"
username is a string for the user name
password is a string for the password
returns FALSE on failure

Example
$db_link = mysql_connect("localhost:3306",
"test", "123");

there is also the persistent mysql_pconnect

Example From PHP Docs
<?php
$link = mysql_connect("localhost", "mysql_user",
"mysql_password")
or die("Could not connect: " . mysql_error());
print ("Connected successfully");
mysql_close($link);
?>

Selecting A Database
mysql_select_db(name, link)
select a database given by the string name
the link is optional and specifies the open link
value such as $db_link returned by a connect
statement.
if not supplied the last opened link is used.
returns TRUE on success else FALSE

Example
mysql_select_db("web_db");

<?php
$lnk = mysql_connect('localhost', 'mysql_user',
'mysql_password')
or die ('Not connected : ' . mysql_error());
// make foo the current db
mysql_select_db('foo', $lnk) or die ('Can't use foo
: ' . mysql_error());
?>

Error Reporting (1)
mysql_error(link)
Return an error string or error number
the link is optional
Empty string is returned if there is no error.

Example
mysql_error();

Error Reporting (2)
mysql_no(link)
Return the error number
the link is optional
0 is returned if there is no error.

Example
mysql_no();

<?php
mysql_connect("localhost", "mysql_user",
"mysql_password");
mysql_select_db("nonexistentdb");
echo mysql_errno() . ": " . mysql_error(). "n";
mysql_select_db("kossu");
mysql_query("SELECT * FROM nonexistenttable");
echo mysql_errno() . ": " . mysql_error() . "n";
?>

Making A Query (1)
mysql_query(query, link)
make a select query (link is optional)
query is a string for the MySQL query
Don't end the query with a semi-colon
Return value is a resource identifier or FALSE if
the query is SELECT, SHOW or DESCRIBE

Example (select all rows of books table)
$query = "SELECT * FROM books";
$result = mysql_query($query);

Making A Query (2)
INSERT and UPDATE queries
for these queries a resource is not returned
TRUE is returned on sucess
FALSE is returned on failure

Example (describe the books table)
$query = "DESCRIBE books";
$status = mysql_query($query);

<?php
$result = mysql_query("SELECT my_col FROM my_tbl")
or die("Invalid query: " . mysql_error());
?>

Retrieving Table Information
mysql_list_fields(database, table, link)
For a select query it retrieves information from
given table in given database. link is optional
The returned resource can be used to obtain
properties of the table such as names of the
table columns and field type information

Example
$fields = mysql_list_fields("web_db",
"books");

Number Of Table Columns
mysql_num_fields(result)
return the numbers of columns in a table
result is the resource returned by a call to the
mysql_list_fields function

Example
$fields = mysql_list_fields("web_db", "books");
$num_columns = mysql_num_fields($fields);

Names Of Table Columns
mysql_field_name(result, index)
return the name of the table column whose
position is given by index (0,1,...)
result is the resource returned by a call to
mysql_list_fields

Example: the first column name
$isbn = mysql_field_name($fields, 0);

<?php
$link = mysql_connect('localhost', 'mysql_user',
'mysql_password');
$fields = mysql_list_fields("database1", "table1",
$link);
$columns = mysql_num_fields($fields);
for ($i = 0; $i < $columns; $i++) {
echo mysql_field_name($fields, $i) . "n";
}
?>

Accessing Table Rows (1)
mysql_fetch_row(result)
each call returns the next row as an indexed
array where result is a resource returned from a
call to mysql_query (FALSE if no more rows)

Example
$row = mysql_fetch_row($result); // row 0
$isbn = $row[0]; // isbn for row 0

mysql_fetch_assoc(result)
as in mysql_fetch_row but next row is returned
as an associative array

Example
$row = mysql_fetch_assoc($result); // row 0
$isbn = $row['isbn']; // isbn for row 0

mysql_fetch_array(result)
combines mysql_fetch_row, mysql_fetch_assoc
returns row information as both an associative
array and an indexed array

Example
$row = mysql_fetch_array($result); // row 0
$isbnA = $row[0]; // isbn for row 0
$isbnB = $row['isbn']; // can also get it this way

Accessing table rows (4)
mysql_num_rows(result)
returns number of rows from a select query
result is the resource returned by the select
query

mysql_affected_rows(result)
used after an INSERT, UPDATE, or DELETE query
to return the number of rows affected
result is the resource returned

Other Functions
mysql_real_escape_string(string,link)
returns a string safe to use in mysql_query

In MySQL 4.1 there are mysqli_... functions
which are supposed to be improved.
There are many other MySQL functions that
we will not use.
See PHP function reference for complete list

Freeing Resources
mysql_free_result(result)
free memory associated with the given resource
called result (after a select query).
Not necessary except for large result sets
Done automatically when script exits.

mysql_close(link)
close the database connection associated with
the given link
doesn't do anything for persistent links.

Processing column names
// Get resource for the field names
// Get number of table columns
$num_cols = mysql_num_fields($fields);
// process them using a for loop
for ($i = 0; $i < $num_cols; $i++)
{
$name = mysql_field_name($fields, $i)
// do something here with $name
}

Processing table rows (1)
while ($row = mysql_fetch_array($result)
{
From SELECT
for ($i = 0; $i < count($row); *i++)
query
{
$col_value = $row[$i]'
// Do something with $col_value here
}
// do end of row processing here
}
// do end of table processing here

Here $row is returned as an array so the inner loop is a
for loop

Processing table rows (2)
while ($row = mysql_fetch_assoc($result)
{
From SELECT
foreach($row as $col_value)
query
{
// Do something with $col_value here
}
// do end of row processing here
}
// do end of table processing here

Here $row is returned as an associated array so the
inner loop is a foreach loop. The foreach is easier to
use.

A db_connect Function
This function can be used in scripts to
connect to a database. Put it in a file called
db_connect.php in your include path
<?php function db_connect($db_name)
{ $host_name = "localhost:3306";
$user_name = "xxxxx"; $password = "yyyyy";
$db_link = mysql_connect($host_name,
$user_name, $password)
or die("Could not connect to $host_name");
mysql_select_db($db_name)
or die("Could not select database $db_name");
return $db_link;
} ?>

Books Display Example (1)
First create the following books.sql file
containing a sample database table
CREATE DATABASE IF NOT EXISTS web_db;
USE web_db;
CREATE TABLE books (
isbn
title
author
pub
year
price
);

CHAR(15)
VARCHAR(100)
VARCHAR(100)
VARCHAR(20)
year
DECIMAL(9,2)

PRIMARY KEY NOT NULL,
NOT NULL,
NOT NULL,
NOT NULL,
NOT NULL,
DEFAULT NULL

books.sql continued (insert some books)
INSERT INTO books VALUES (
'0-672-31784-2',
'PHP and MySQL Web Development',
'Luke Welling, Laura Thomson',
'Sams', 2001, 74.95
);

Insert a few more (see simplebooks.sql)

Run books.sql through MySQL using the
command
mysql -u xxxxx -p < c:/.../books.sql
Or use the gui client MyCC
here xxxxx is your MySQL username and the -p
option means to prompt for the password
Now write a PHP script called dbase.php that
displays the books in an HTML table

dbase.php (1)
HTML header information
<?php require_once("db_connect.php"); ?>
<html>
<head>
<title>
Displaying the book database table using PHP
</title>
<h1>Displaying thebook database table using PHP</h1>
<?php

dbase.php (2)
Make a database connection
$db_link = db_connect("web_db");

This uses the function defined in the include
file db_connect.php
My include path in php.ini is
include_path=".;c:Apachephpincludes"
current directory

dbase.php (3)
Send a SELECT query for all columns
$result = mysql_query($query)
or die("SQL Query failed");

Obtain table properties
$num_columns = mysql_num_fields($fields)

dbase.php (4)
Display column headings in an HTML table
echo '<table border="1">', "n";
echo "<tr>n";
for ($i = 0; $i < $num_columns; $i++)
{
echo "<th>", mysql_field_name($fields, $i),
"</th>n";
}
echo "</tr>n";

dbase.php (5)
Display the books table in as an HTML table
while ($row = mysql_fetch_assoc($result))
{
echo "<tr>n";
foreach ($row as $col_value)
{
echo "<td>$col_value</td>n";
}
echo "</tr>n";
}
echo "</table>n";

dbase.php (6)
Free resources and close connection
mysql_free_result($result);
mysql_close($db_link);
?>
</body>
</html>

view script dbase.php
http://localhost/users/MYSQL/dbase.php

Calling Script From Button (1)
Give the button a name and a value
<input type="submit" name="choice" value="Display">

When form is submitted the name will exist
if (isset($_REQUEST['choice'])
{
// process the button click here
}
...

Multiple submit buttons should have different
names or same name, different values

Calling Script From Button (2)
Another approach is to use the submit button
label (value) to distinquish choices
$choice = isset($_REQUEST['choice']) ?
$_REQUEST['choice'] : "";
if ($choice == "Display")
{
// process the button click here
} ...

Multiple submit buttons can have the same
name but different labels (values)

Calling Script From Link
A link can be clicked to invoke the script
again or to pass a parameter to it using the
GET method (query string in link)
<?php
$this_url = $_SERVER['PHP_SELF'];
$edit_url = "$this_url?choice=edit&id=$id";
$delete_url = "$this_url?choice=delete&id=$id";
?>
<a href="<?php echo $edit_url?>">[ Edit ]</a>
<a href="<?php echo $delete_url?>">[ Delete ]</a>

Suggestion Box
Users make suggestions through a textarea
in a form and submit them
Suggestion is saved in a MySQL database
table called sbox in database web_db
Suggestions are displayed along with the
time
view script sbox/sbox.php
http://localhost/php/MYSQL/sbox/sbox.php

Suggestion Box Display

initial
display

display
when
submit link
is clicked

sbox.sql
CREATE DATABASE IF NOT EXITS web_db;
USE web_db;
DROP TABLE IF EXISTS sbox;
CREATE TABLE sbox
(
id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
time DATETIME NOT NULL,
suggestion TEXT NOT NULL
);

view script sbox/sbox.sql

Script Logic
IF request for new suggestion THEN
display form to get new suggestion
ELSE
IF form was submitted THEN
insert suggestion into database table
ENDIF
Retrieve suggestions from database table
IF there are suggestions THEN
display them
ELSE
Suggestion table is empty
ENDIF
ENDIF
provide self link to enter a new suggestion

sbox.php (1)
<?php require_once("db_connect.php"); ?>
<html><head><title>Suggestion Box</title></head>
<body><h1>Suggestion Box</h1>
<?php
$self = $_SERVER['PHP_SELF'];
if (isset($_REQUEST['new'])) // link was clicked
{ ?>
<form action="<?php echo $self ?>" method="POST">
Enter your suggestion:<br>
<textarea name="suggestion" rows="5" cols="50"
</textarea><br>
<p><input type="submit" name="add"
value="Submit"></p>
</form>
<?php }

sbox.php (2)
else
{
if (isset($_REQUEST['add']))
{
$suggestion = $_REQUEST['suggestion'];
$query = "INSERT INTO sbox SET time=NOW(),"
. "suggestion='$suggestion'";
mysql_query($query);
}

Forgot to use addslashes and stripslashes

sbox.php (3)
// Display all the suggestions
$query = "SELECT time, suggestion FROM sbox";
if (mysql_num_rows($result) > 0)
{
{
$time = $row['time'];
$suggestion = $row['suggestion'];
echo "<b>$time:</b> $suggesion<br>n";
}
}
else

sbox.php (4)
{
echo "The suggestion box is empty";
}
?>
<p><a href="<?php echo $self ?>?new=1">
Submit a new suggestion</a></p>
</body>
</html>
<?php
}
A trick for
?>
calling a
script from a
link with a
view script sbox/sbox.php
parameter

Other Versions
There are versions sbox2, sbox3, sbox4
sbox2 handles quotes and HTML text properly
sbox3 adds error checking
sbox4 is a simpler version of sbox3 for which the
form is always displayed so no link is needed to
add a new suggestion.

sbox4.php (1)
<?php
require_once("db_connect.php");
$self = $_SERVER['PHP_SELF'];
?>
<html><head><title>Suggestion Box</title></head>
<body><h1>Suggestion Box</h1>
<form action="<?php echo $self ?>" method="POST">
Enter your suggestion:<br>
<textarea name="suggestion" rows="5" cols="50"
</textarea><br>
<p><input type="submit" name="add"
value="Submit"></p>
</form>

sbox4.php (2)
<?php
// add a new suggestion if there is one
if (isset($_POST['add']))
{
$suggestion = addslashes($_POST['suggestion']);
if (strlen($suggestion) > 0)
{
$query = "INSERT INTO sbox SET time=NOW(),
suggestion='$suggestion'";
mysql_query($query);
}
}

sbox4.php (3)
// display all the suggestions
$query = "SELECT time, suggestion FROM sbox ORDER
BY time DESC";
if (mysql_num_rows($result) > 0)
{
{
$time = $row['time'];
$suggestion = htmlspecialchars(stripslashes(
$row['suggestion']));
echo "<strong>$time:</strong> $suggestion<br>
n";
}
}

sbox4.php (4)
else
{
echo "The suggestion box is empty";
}
?>
</body>
</html>

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