PHP Documentation

MySQL Documentation

PHP Documentation regarding MySQL

characters:
  cslab103.cs.edinboro.edu - web server
  form.htm - web (HTML) form (file containing form)
  processForm.php - php file to process submitted data
                                from form.htm

An end-user's web browser issues an HTTP request to a web server ("cslab103.cs.edinboro.edu") for a particular web page ("form.htm").

The web server ("cslab103.cs.edinboro.edu") sends the web page ("form.htm") to the end-user's web browser and the browser interprets the HTML codes to display the page in the browser window.

The end-user fills in the form fields and submits the form issuing an HTTP request to a web server ("cslab103.cs.edinboro.edu") to run a CGI script ("processForm.php").

The web server ("cslab103.cs.edinboro.edu") starts the CGI script ("processForm.php").  

The CGI script ("processForm.php") opens a connection with the MySQL server and sends the MySQL commands.

The MySQL server receives the MySQL commands, processes them, and sends results back to the CGI script ("processForm.php").

The CGI script ("processForm.php") interprets the results and creates an HTML document to submit to the web server ("cslab103.cs.edinboro.edu").

The web server ("cslab103.cs.edinboro.edu") sends the CGI generated web page to the end-user's web browser and the browser interprets the HTML codes to display the response page in the browser window.

1. Check and filter the data coming from the end-user
2. Set up a connection to the appropriate database
3. Determine the database command to execute
4. Execute the commands
5. Retrieve the results
6. Prepare retrieve data for XHTML processing
7. Present the results back to the end-user as an XHTML web page

trim($variable) - removes all whitespace in front and after value contained in $variable

if (!$variable1  || !$variable2 ...) - checks whether the variables have a value

$variable = addslashes($variable) - "escapes" any special characters for MySQL (ex: " (double quote) becomes \" )

Prepare data retrieved from the database to be put into XHTML:

$variable = stripslashes($variable) - removes slashes used by MySQL for display in HTML ( \" becomes " )

$variable = htmlspecialcharacters($variable) - "encodes" special characters for use in HTML ( < becomes &lt )
 

@ $link = mysql_connect( "<host>", "<username>", "<password>");  
               //connects to MySQL

    if (!$link)
    {
        print( " ERROR connecting to db.  Please try again later. <br>");
        exit;
    }

mysql_select_db(<database name>);      // connects to a db

myql_close( $link);

Example:

@ $link=mysql_connect(      
                     "cslab103.cs.edinboro.edu",
                      "zimmer", "mypw");  
                       //connects to MySQL

    if (!$link)
    {
        print( " ERROR connecting to db.<br>");
        exit;
    }

mysql_select_db("test"); // connects to a db
myql_close( $link);

$query = <valid MySQL query>;

$results = mysql_query($query);  
              // queries the open database

        or

$results = mysql_db_query($db, $query, $link);  
              // don't need to select the db from above
 

Example:

$query ="SELECT * FROM courses";
$results = mysql_query($query);

or

$query = "INSERT INTO courses VALUES
               ('csci125', 2,'Bennett', 3)";
$results = mysql_query($query);
 

$results = mysql_query($query);  
              // queries the open database

$num_results = mysql_num_rows($results);

    for ($i=0; $i<$num_results; $i++)
    {
        // process the results

        $row = mysql_fetch_array($results); 
                 //assigns a row to $row

        print ("<br> $row["<fieldname>"]...<br>");
    }
 

Example:

$query ="SELECT * FROM courses";
$results = mysql_query($query);
$num_results = mysql_num_rows($results);
for ($i=0; $i<$num_results; $i++)
{
    $row = mysql_fetch_array($results); 
    print ("<br> $row[num] $row[instr]...<br>");
}
 

$results = mysql_query($query);  
              // queries the open database

$num_results = mysql_affected_rows(); 

    if ($results)
    {
        print("<br>$num_results record was added.<br>\n");
     }

Example:

$query = "INSERT INTO courses VALUES
               ('csci125', 2,'Bennett', 3)";
$results = mysql_query($query);
$num_results = mysql_affected_rows( );
if ($results)
{
    print("<br>$num_results rows added.<br>\n");
}