Interface of PHP with DataBases
by yung

This is a quick guide for you to learn about about the interaction with
MySQL databases that can be done from PHP scripts. From this guide we're
assuming that you have knowledge on how to use SQL code, we are also
assuming you already have some knowledge on php scripting. For more
information on MySQL you could visit www.mysql.com and for php you could
read our PHP lecture or go to www.php.net.

Examples of what can be done with PHP and MySQL:

Connecting to a Server: mysql_connect("your.domain.com", "login",
"password");
This command will cause the service of PHP to connect to the host of your
choosing, and login with the login/password information given. You won't
need to worry about the web users of seeing your password, PHP processes
the information before it is sent to client side. This instruction must
be used before using any other instruction related to MySQL on PHP.

Example: Let's think that your domain is "no.domain.com", and your username
for your MySQL database is "yung" and the password ir "letsgo". Then you can
use the following code to connect:
<?
$result=mysql_connect("no.domain.com","yung","letsgo");
?>

Consulting the Server: mysql_db_query("database name", "MySQL Query");
This command will perform a query to the MySQL database. The results are
usually stored on a variable so that they can be accessed later for
displaying on the web page.
Example: To execute a query on a database called "data", we must first
select all the data from the table "local_data" and put them on a
variable called $result, we can do this by executing the following line of
code on our web pages:
<? $result = mysql_db_query("data", "select * from local_data");
?>

Converting the data into PHP array data: mysql_fetch_array($result);
This command will convert all the results from the MySQL query into PHP 
for easier management of data. $result should be the variable where you
stored the MySQL query results.
Example: To convert the data that was stored on a variable called $result
and storing the converted data on an array variable called $rows, we should
execute the following command:
<? $rows = mysql_fetch_array($result); ?>

Counting the selected data: mysql_num_rows($result);
This command will return the number of rows/lines of data that have been
stored via a query. The result of the command mysql_num_rows is usually 
putten on a variable to be used on a structured cycle. $result should be 
replaced with the name of the variable where you have stored all the results 
of the query using the command mysql_db_query.
Example: To retrieve the number of rows returned on a query that returns
your results on a variable called $result, and store this value on a
variable called $num_rows, you'll have to use the following command:
<? $num_rows = mysql_num_rows($result); ?>

Obtaning the number of fields used: mysql_num_fields($result);
The command mysql_num_fields can be used to obtain the number of fields that
result from a MySQL query. This value is usually assigned to a variable for
use on a cycle. $result should be replaced with the name of the variable of
your choice that stores the result of a query that has been performed
earlier.
Example: To obtain the number of fields returned on a query which results
were stored on a variable called $result, and storing the value on a
variable called $num_fields, you should use the following command:
<? $num_fields = mysql_num_fields($result); ?>

Displaying information: echo $variable;
This command is used to display the value of a variable on the web page.
$variable should be replaced with the name of the variable that you desire
to display. Also can be used in conjunction with mysql_results to display on
HTML pages.
Example: To display the content of a variable $num_rows to a page, you
should use the following command in the page where you desire to display it:
<? echo $num_rows; ?>

Displaying Results: mysql_result($result, 0, "Description");
This command is used to determine the value of a specific row and field that
has been resulted from a query.
Example: To return the value of a field called "LastName" from the first row
of results of a query that has been stored on $result, you should use the
following command:
<? echo mysql_result($result,0,"LastName"); ?>

Putting everything together:

The lines that start with a # are comments, were it should explain what
we're trying to do on a specific line of code.

<?php
  #Enter PHP mode

  $link = mysql_connect ("www.smart-dev.com", "http", "http") or die ("Couldn't connect");
  #assign $link true or false: true if we connect to www.smart-dev.com and
  #MySQL accepts http as our login and password
  # the "or die" assures that PHP doesn't execute if the result is false.

  print ("Connection Successful");
  #If we haven't "killed" PHP execution, display "Connection Successful" on browser

  $result = mysql_query("select * from http.data");
  #Query all fields (select *) from the database httpd on
  #the table data and assign the output to the variable $result

  ?><TABLE WIDTH="100%" BORDER=2> <?
  #Stepping out of PHP, display table, and enter PHP mode again
  #This is not the only way to write HTML on PHP, but it's the easier way

  while($row = mysql_fetch_array($result)) {
  #Transform our results to an array of PHP data called $row
  #The mysql_fetch stores a counter of each value read from the results
  #The first time will read "1 yunix 5063 0"
  #Second time will read "2 fiber 2254 1" 
  #and so on until it has read all the table "data"
  #$row will have a array of values for each row read.

    ?><TR>
      <TD><?echo $row[0];></TD><?
    ?><TD><?echo $row[1];></TD><?
    ?><TD><?echo $row[2];></TD><?
    ?><TD><?echo $row[3];></TD><?
    ?><TD><?echo $row[5];></TD><?
    ?><TD><?echo $row[6];></TD>
    </TR><?
  #Exit PHP for each field of the row of data and display the field.
  #you can also use $row["NameOfField"] instead of the numbers.

  }
  #while execution finishes, it goes back to the while
  #if there's still something to process.

  ?></TABLE><?
  #Exit PHP, finish table, Enter PHP
 
  mysql_free_result($result);
  #freeing $result

  mysql_close ($link);
  #Close link to database

?>
#Exit PHP