PHP: Part II
Please note that there will be
No homework
you can experiment with php and MySQL on your i5
account
Attribution
These slides are based on:
-Ethan Cerami:
http://ecerami.com/mysql/
1
Road map
• Php II
• Using MySQL and php on i5
Working with Strings
• You can concatenate two strings
together via the . operator. For
example:
$sequence1 = "cagtaagtga";
$sequence2 = "agatgtgcgt";
$sequence3 = $sequence1 . $sequence2;
Working with Strings
• PHP provides lots of built-in functions for
manipulating strings. For example:
– strtolower
-- Make a string lowercase
– strtoupper -- Make a string uppercase
– trim -- Strip whitespace from the beginning and end of a string
– strlen -- Get string length
– strrev -- Reverse a string
•
Go to:
http://us4.php.net/manual/en/ref.strings.php
for a full list of string manipulation functions.
•Mathematical Functions
• PHP provides lots of built-in mathematical functions.
For example:
– abs
-- Absolute value
– cos -- Cosine
– decbin -- Decimal to binary
– dechex -- Decimal to hexadecimal
– decoct -- Decimal to octal
– deg2rad -- Converts the number in degrees to the radian equivalent
– floor -- Round fractions down
– log10 -- Base-10 logarithm
– log -- Natural logarithm
– max -- Find highest value
– min -- Find lowest value
– pow -- Exponential expression
– rand -- Generate a random integer
– sin -- Sine
– sqrt -- Square root
– tan -- Tangent
•Arrays
• An example array:
$fruit = array ("apples", "oranges", "bananas");
echo "<P>Fruit: $fruit[1]"; // This prints Oranges
• Note: just like ordinary variables, each space
in an array can contain any type of value.
• For example, this is considered legal in PHP:
$numbers = array ("zero", 1, "two");
• Associative Arrays
• PHP also supports associative arrays.
• With associative arrays, you can use strings as
indexes.
• It's called associative because it associates values
with meaningful indices.
•
You can think of an associative array as a look-up
table.
• For example, you might have an associative array of
organisms which maps common names to species
names.
• If you request the element with the key “human”,
you get back the value “Homo Sapiens”.
Reusable PHP Components
•
• It’s very easy to create reusable PHP components that
can be used by multiple web pages.
• For example, your web site might include two components:
header.php and footer.php.
• All pages in you web site can include these two
components.
• If you want to update the header, just update the header
component, and the change automatically appears on all
pages.
• Main advantages of reusable components:
– much easier to maintain
– more modular web site structure
Reusable PHP Components
The PHP Include Statement
(run)
Accessing Form Data in PHP(run)
• Accessing form data in PHP is very simple.
• Simply query the $_GET variable
(or the $_REQUEST variable)
for the form parameter you want.
“Big Picture”: PHP and MySQL
• PHP Includes built-in support for accessing
multiple databases, including Oracle, Microsoft
SQL Server, MySQL, etc.
• PHP support for MySQL is both simple and
comprehensive.
• PHP support for MySQL is fully documented
here:
– http://us2.php.net/manual/en/ref.mysql.php
– (Official Reference Page)
Accessing MySQL: Overview
• To Access MySQL from a PHP Script, you generally follow the same four step
process:
– Step 1: Make a connection to the MySQL database server.
• this requires that you specify the location of the database, plus a user
name and password.
– Step 2: Select the database within MySQL that you want to work with.
• for example, you may want to select the “ensmartdb” database we
created in Class #1.
– Step 3: Issue a SQL Statement
• this could be any valid SQL statement, e.g. SELECT, INSERT, UPDATE,
DELETE.
– Step 4: If you are issuing a SELECT statement, iterate through the result
set and extract each record.
• for example, extract specific fields in each record, and output as HTML.
• At each step, check for specific error conditions. If an error occurs, fail
gracefully and inform the user of the problem.
Accessing MySQL: Overview
Step 1: Connect to MySQL
• Before you can retrieve data from a MySQL table, you must first
connect to the MySQL database server.
• To connect, you use the msql_connect function.
mysql_connect (address, user_name, password);
– Here, address is the IP address or host name of the computer where
the MySQL server is actually running.
– If you are connecting to a MySQL server running on your local
machine, the address should be set to “localhost”.
• For example:
$connection = mysql_connect("localhost", ”username", ”password");
Accessing MySQL: Overview
Step 1: Connect to MySQL
Connection Errors
• The mysql_connect function is not guaranteed to work. For
example:
– the database server might be down, or
– the database server might be on a different machine, and the
network connection is down.
• It is important to test for these types of errors so that you can
report meaningful error messages to your users.
• If the connection attempt succeeds, the mysql_connect function
will return a number that identifies the connection to the
database.
• If the connection attempt fails, the mysql_connect function will
return false.
• Therefore, if mysql_connect returns false, you know something has gone
awry.
The @ Error Suppressor
• Suppose we have the following code
with an invalid user name/password:
$connection = mysql_connect ("localhost", ”demo", ”demo");
•
By default, the mysql_connect will
display a detailed error message
directly to the user
• However, you may want to present a more user-friendly error message to your
users.
• To suppress error messages from automatically appearing, use the @ error
suppression operator directly before the function call.
• For example:
$connection = @mysql_connect("localhost", ”demo", ”demo");
• Then, explicitly check the return value of mysql_connect (see next slide).
Connecti
•Connection Errors
• if mysql_connect returns false, you know something has gone
wrong.
• To determine exactly what went wrong, you can use the
mysql_error function.
•
You can therefore create your own custom error page.
• For example:
// Connect to the Database.
// The @ character will suppress default error messages.
$connection = @mysql_connect("localhost", ”guest", ”guest");
// If we fail to connect, display an error message and exit.
if ($connection == false) {
echo ("Unable to connect to the database server.");
die ("<P>MySQL Error: " . mysql_error());
}
Side Note: the die() function
• The die() function will output a specific
error message, and then stop processing
of the PHP script.
– Any remaining PHP code is simply ignored.
• Very useful for reporting error
messages to the user.
Step 2: Select a Database
• This part is easy. To select a database, use the
mysql_select_db function.
• Just like mysql_connect, mysql_select_db will return false if an
error occurs.
• Sample Code:
// Select the correct database.
// The @ character will suppress default error messages.
$selection = @mysql_select_db("ensmartdb");
// If we fail to select, display an error message and exit.
if ($selection == false) {
echo ("Unable to select database.");
die ("<P>MySQL Error: " . mysql_error());
}
Step 3: Issue a SQL Statement
• To issue a SQL statement, use the mysql_query
function. For example:
$result = mysql_query ("SELECT * from organism");
• As usual, if an error occurs, mysql_query will return
false
Step 4: Iterate through the SQL Result Set
• If you have issued a SELECT statement, you want to iterate through all
the records in your result set.
•
To do so, use the mysql_fetch_array function along with a while loop.
• Each time you call mysql_fetch_array, you get back a row variable
corresponding to a single record in the result set.
• This row variable is
an associative array, which
will contain all the field
data for a record.
• Note: You can access array
elements by key strings or
by index value.
Case study #1 (run)
Step 1: Connect
Check for errors
Step 2: select DB
Check for errors
Case study #1 continued …
Step 3: issue SQL
statement
Check for errors
Step 4: Iterate
through result set
Accessing MySQL on i5.nyu.edu
To use MySQL on i5.nyu.edu:
• Logon to i5.nyu.edu.
• Then connect to your own database using
mysql -u <netid>
• Once you are at the mysql prompt,
then you need to type:
use <netid> to continue
Here are some notes about writing and running MySQL
scripts and using MySQL on i5.nyu.edu:
• you may place your MySQL scripts in your home
directory
• use Pico or vi to edit the script
• use ";" at the end of a script line or command
• save your script file with an ".sql" suffix
Here are some commands to try on i5.nyu.edu:
$ mysql -u <netid> <netid>
mysql> use <netid>
mysql> create table book (
-> title varchar(32),
-> author varchar(64)
-> );
[Result should be: Query OK. 0 rows affected.]
mysql> insert into book values ('Pride and Prejudice', 'Jane
Austen');
[Result should be: Query OK. 1 row affected]
mysql> select * from book;
[Result should show the name and author and 1 row in set]
mysql> exit
[Result should show Bye -> and return you to the Unix
To see review of Mysql commands:
http://cs.nyu.edu/courses/spring04/V22.0380-001/MysqlSummary.htm
Here are some notes about writing
and running PhP with MySQL on
i5.nyu.edu:
1. Your_php_script must be located in
public_html/cgi-bin
2. The first line of your PHP script has the
directive: #!/usr/local/bin/php
3. Use chmod 755 <filename.php> in order for it to
be world-executable.
4. Your database name is the same as your netid.
Lets look at the following Examples
based on these 2 sql scripts
(creating 2 tables)
• recordings_script.sql (creating 1 table)
• composers_script.sql (creating 1 table)
• php_mysql6.php script (run sql queries)
• HTML Form: http://i5.nyu.edu/%7Edse7916/php_mysql6.html
• Full example on this page (implantation for i5
accounts):
• http://cs.nyu.edu/courses/spring04/V22.0380001/PhpMysqlTogetherSummary.htm
composers_script.sql
DROP TABLE IF EXISTS composers;
CREATE TABLE composers ( composer_name varchar(32)
NOT NULL, century integer(2) DEFAULT 0, origin
varchar(15), PRIMARY KEY(composer_name));
INSERT INTO composers VALUES ("Beethoven", 19,
"German"); INSERT INTO composers VALUES ("Handel",
18, "British"); INSERT INTO composers VALUES ("Verdi",
19, "Italian"); INSERT INTO composers VALUES
("Tchaikovsky", 19, "Russian");
INSERT INTO composers VALUES ("Copland", 20,
"American");
INSERT INTO composers VALUES ("Bach", 18, "German");
INSERT INTO composers VALUES ("Bizet", 19, "French");
recordings_script.sql
DROP TABLE IF EXISTS recordings;
CREATE TABLE recordings ( title varchar(32) NOT NULL, composer_name
varchar(32) NOT NULL, medium varchar(5), price decimal(6,2),
year_recorded int(4), music_type varchar(10), PRIMARY KEY(title),
FOREIGN KEY(composer_name) REFERENCES composers
(composer_name));
INSERT INTO recordings VALUES ("Symphony
#9","Beethoven","CD",15.99,1998,"Orchestral");
INSERT INTO recordings VALUES ("Sleeping
Beauty","Tchaikovsky","DVD",34.99, 1992, "Ballet");
INSERT INTO recordings VALUES ("La Traviata","Verdi","Video",29.99,
2001, "Opera"); INSERT INTO recordings VALUES
("Carmen","Bizet","Video",34.99, 1982, "Opera");
INSERT INTO recordings VALUES ("Symphony #4","Tchaikovsky","CD",
10.99, 1998, "Orchestral"); INSERT INTO recordings VALUES ("Tocatta
& Fugue","Bach","CD", 21.95,1997,"Orchestral");
INSERT INTO recordings VALUES ("Fidelio","Beethoven","DVD",49.99,
1991,"Opera"); INSERT INTO recordings VALUES ("Appalachian
Spring","Copland","Video",19.99, 2000,"Orchestral");
INSERT INTO recordings VALUES ("Il Trovatore","Verdi","DVD",44.99,
1990, "Opera"); INSERT INTO recordings VALUES ("Swan
Lake","Tchaikovsky","Video",14.99,1982,"Ballet");
#!/usr/local/bin/php
// example using php and mysql on i5.nyu.edu
<HTML>
<head>
<title>PHP: Sample Form </title>
</head>
<body bgcolor = lightblue>
<h2>Composers on File </h2>
<p>
<?php
/* Connecting, selecting database on i5.nyu.edu*/
$link = mysql_connect("", “your_netid", "") or die("Could not connect : " . mysql_error());
/* echo "Connected successfully"; -- for testing purposes */
mysql_select_db(" your_netid ") or die("Could not select database");
/* setting a variable for the nation of origin on the HTML form */
$country = $_POST['country'];
/* Performing SQL query */
$query =
"SELECT a.title, a.composer_name,a.music_type
FROM recordings a, composers b
WHERE a.composer_name = b.composer_name AND origin='$country'
ORDER BY a.title ";
$result = mysql_query($query) or die("Query failed : " . mysql_error());
(… continued on next page….)
/* … continued…. see how many records are returned */
$num_rows = mysql_num_rows($result);
if ($num_rows > 0) {
/* Printing results in HTML */
echo "<table>\n";
while ($line = mysql_fetch_array($result, MYSQL_ASSOC)) {
echo "\t<tr>\n";
foreach ($line as $col_value) {
echo "\t\t<td>$col_value</td>\n";
} // end of foreach
echo "\t</tr>\n";
} // end of while
echo "</table>\n";
echo "<i>\n\n $num_rows records match this query.\n </i>";
} else {
echo "There were no results that match this query. Please try again.\n";
}
/* Free resultset */
mysql_free_result($result);
/* Closing connection */
mysql_close($link);
?>
</body>
</html>
Where to get more info. On PHP
• When you get stuck, there are three places
to check first:
– Check the PHP Manual at:
http://www.php.net/docs.php
– Check the PHP FAQ at:
http://www.php.net/FAQ.php
– If you want information about a specific function,
go to:
http://www.php.net/function_name. For
example:
• For information about echo, go to: http://php.net/echo
• For information about phpinfo, go to:
http://php.net/phpinfo
Acknowledgements
• • Information contained in these slides is based
– on these sources:
•
•
•
•
•
•
•
•
•
•
– W3 Schools PHP Tutorial.
http://www.w3schools.com/php/default.asp
– Kevin Yank, “Building a Database-Driven Web Site
Using PHP and MySQL” (SitePoint).
http://dev.mysql.com/techresources/
articles/ddws/
– Rasmus Lerdorf, “PHP Pocket Reference” (O’Reilly
& Associates).
http://www.oreilly.com/catalog/phppr/chapter/php
_pkt.html
Deena Engel course webiste:
http://www.cs.nyu.edu/courses/spring04/V22.0380-001/PhpSummary.htm