1. LIS651 lecture 7 PHP mySQL Thomas Krichel 2010-03-11

2. PHP mySQL functions We are using here the new version of PHP mySQL function, starting with mysqli_ The interface is object-oriented, but can also be accessed in a non-object-oriented way. This is known as the procedural style, in the documentation. You should use the online documentation at http://php.net/mysqli

3. error suppression The function mentioned in this library usually report any error that has occurred. It can be useful to suppress such errors with the PHP error suppression operator @. @function() will run the function function without reporting mistakes. You can then create your own customized mistakes by checking for errors every time you run a mysqli function. This is useful.

4. mysqli_connect()‏ This is used to establish a connection to the mySQL server. It is typically of the form mysqli_connect('host', 'user', 'password'); Example $link= mysqli_connect('localhost','boozer','heineken'); You can use localhost as the host name for wotan talking to itself, but you could also connect to other Internet hosts, if you have permission.

5. the mySQL connection with mysqli The mysqli module has the ability to handle several connections to the mySQL server. Once a connection is established it is represented by the variable returned by mysqli_connect(). This variable, of type "resource" has the be referenced later to let mysqli functions know what connection you are using, because there may be more than one open at the same time.

6. mysqli_connect_error()‏ This function returns a string with the last connection error. $link = mysqli_connect("localhost", "bad_user", ""); if (!$link) { print "Can't connect to localhost. The error is "; print mysqli_connect_error(); print " "; } Note the use of ! to express Boolean "not".

7. mysqli_error( link )‏ This function return the error from the last mySQL command. It returns false if there was no error. $error=mysqli_error($link); if($error) { print "mySQL error: $error "; } This function requires the connection as a parameter. The value returned from that function is a simple string. It is a good idea to check out error messages.

8. mysqli_select_db()‏ This command has the syntax where link is a resource representing a connection and database is the name of a database. This tells mySQL that you now want to use the database database. mysqli_select_db($link,'beer_shop'); It has the same effect as issuing USE beer_shop; within mySQL.

9. mysqli_query()‏ mysqli_query(link,query) send the query string query to mySQL connection represented by link $link = mysqli_connect("localhost", "owner", "bruch"); // you may then add some connection checks $query="SELECT * FROM beer_shop.customers"; $result=mysqli_query($link,$query); Note that the query itself does not require a terminating semicolon. The result is in $result.

10. result of mysqli_query()‏ For SELECT, SHOW, DESCRIBE or EXPLAIN mySQL queries, mysqli_query() returns a resource that can be further examined with mysqli_fetch_array(). This is very important function that we look at in the next slide. For UPDATE, INSERT, DELETE, DROP and others, mysqli_query() returns a Boolean value.

11. examining resulting rows mysqli_fetch_array(result) returns an array that is the result row for the resource result representing the most recent, or NULL if it the last result is reached. Its results in an array that contains the columns requested both by number and by column name: while($columns=mysqli_fetch_array($result)) { print 'name: '.$columns['name']; print 'first column: ‘.$columns[0]; }

12. examining a specific result mysqli_data_seek(result, number) sets the array that is returned by mysqli_fetch_array to a number number. while($row=mysqli_fetch_array($result)) { print 'first column: '.$row[0]; } mysqli_data_seek($result,0); // otherwise the second loop would not work while($row=mysqli_fetch_array($result)) { print 'first column: '.$row[0]; }

13. mysqli_num_rows()‏ This command has the syntax mysqli_num_rows(result) where the resource result is the result of a query. It returns the number of rows that are in the result. This is useful in announcing the number results before display of results.

14. mysqli_real_escape_string()‏ mysqli_real_escape_string( link,string) returns a string escaped for the using in mySQL. $name="John O'Guiness"; $s_name=mysqli_real_escape_string($link,$name); print $s_name; // prints: John O\'Guiness Note that this function makes a call to mySQL, therefore a connection must be established before the function can be used. This function guards against SQL injections.

15. mysqli_close(link)‏ This command closes a connection. It requires the connection as an argument, so that it knows which connection to close. This is the happiest command there is, because it means that we have finished. Unfortunately it is not used very often because the mySQL connection is closed automatically when the script finishes running.

16. extra: sha1()‏ This is a function that calculates a combination of 40 characters from a string. The result of sha1() can not be translated back into the original string. This makes it a good way to store password. $s_password=sha1($password);

17. http://openlib.org/home/krichel Thank you for your attention! Please switch off machines b4 leaving!