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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/

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 (r un ) The PHP Include Statement

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 Step 4: Iterate through result set Check for errors

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 command line prompt.]

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: Your_php_script must be located in public_html/cgi-bin The first line of your PHP script has the directive: #!/usr/local/bin/php Use chmod 755 <filename.php> in order for it to be world-executable. 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/V22.0380-001/ 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

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