The document discusses using PHP to summarize documents in 3 sentences or less that provide the key information. It discusses two main ways to pass variables and values to a PHP script - using hidden HTML inputs or appending values to the PHP script's URL. It also discusses updating an example script to provide edit and delete links that pass a user's ID to the handling pages.

1. Sending Values
Manually
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In the examples so far, all of the data received in the PHP script came from
what the user entered in a form. There are, however, two different ways
you can pass variables and values to a PHP script, both worth knowing.
The first method is to make use of HTML's hidden input type:
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The second method is to append a value to the PHP script's URL:
This technique emulates the GET method of an HTML form. With this
specific example, page.php receives a variable called $_GET['name'] with a
value of Brian.
To demonstrate this GET method trick, a new version of the view_users.php
script will be written. This one will provide links to edit or delete an existing
user. The links will pass the user's ID to the handling pages, both of which
will be written subsequently.
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Step 2
Change the SQL query as follows.
We have changed this query in a couple of ways. First, we select the first
and last names as separate values, instead of as one concatenated value.
Second, we now also select the user_id value, which will be necessary in
creating the links.
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Step 3
Add three more columns to the
main table.
In the previous version of the
script, there were only two
columns: one for the name and
another for the date the user
registered. We've separated
out the name column into its
two parts and created one
column for the Edit link and
another for the Delete link.
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Step 4
Change the echo statement within
the while loop to match the table's
new structure.
For each record returned from
the database, this line will print
out a row with five columns. The
last three columns are obvious
and easy to create: just refer to
the returned column name.
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For the first two columns,
which provide links to edit or
delete the user, the syntax is
slightly more complicated. The
desired end result is HTML
code like <a
href="edit_user.php?id=X">Edi
t</a>, where X is the user's ID.
Having established this, all we
have to do is print
$row['user_id'] for X, being
mindful of the quotation marks
to avoid parse errors.
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Using Hidden Form
Inputs
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Step 1
Create a new PHP document in your text editor or IDE.
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Step 2
Include the page header. This document will use the same template system
as the other pages in the application.
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Step 3
Check for a valid user ID value.
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Step 4
Include the MySQL connection script.
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Step 5
Begin the main submit conditional.
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Step 6
Delete the user, if appropriate.
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Step 7
Check if the deletion worked and respond accordingly.
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Step 11
Display the form. First, the database information is retrieved using the
mysql_fetch_array() function. Then the form is printed, showing the name
value retrieved from the database at the top. An important step here is
that the user ID ($id) is stored as a hidden form input so that the
handling process can also access this value.
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11. Editing Existing
Records
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Step 1
Create a new PHP document in your text editor or IDE.
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Step 3
Include the MySQL connection script and begin the main submit conditional.
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Step 4
Validate the form data.
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Step 6
Update the database.
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Display the form. The form has but three text inputs, each of which is made
sticky using the data retrieved from the database. The user ID ($id) is stored
as a hidden form input so that the handling process can also access this
value.
Paginating Query
Results
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Step 2
After including the database connection, set the number of
records to display per page.
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Step 3
Check if the number of required pages has been determined.
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Step 4
Count the number of records in the database.
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Step 5
Mathematically calculate how many pages are required.
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Step 6
Determine the starting point in the database.
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Step 7
Change the query so that it uses the LIMIT clause.
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Step 12
After completing the HTML table, begin a section for displaying links
to other pages, if necessary.
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Step 13
Finish making the links.
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21. Making Sortable
Displays
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Step 1
Open or create view_users.php in your text editor or IDE.
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Step 3
Check if a sorting order has already been determined.
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Step 4
Begin defining a switch conditional that determines how the
results should be sorted.
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Step 5
Complete the switch
conditional. There are six
total conditions to check
against, plus the default
(just in case). For each the
$order_by variable is
defined as it will be used in
the query and the
appropriate link is
redefined. Since each link
has already been given a
default value (Step 2), we
only need to change a
single link's value for each
case.
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Step 6
Complete the isset() conditional.
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Step 7
Modify the query to use the new $order_by variable.
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Step 8
Modify the table header echo statement to create links out of the column
headings.
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Step 9
Modify the echo statement that creates the Previous link so that the sort
value is also passed.
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Step 10
Repeat Step 9 for the numbered pages and the Next link.
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Understanding HTTP
Headers
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HTTP (Hypertext Transfer Protocol) is the technology at the heart of the World
Wide Web because it defines the way clients and servers communicate (in
layman's terms).
PHP's built-in header() function can be used to take advantage of this protocol.
The most common example of this will be demonstrated here, when the
header() function will be used to redirect the Web browser from the current
page to another.
To use header() to redirect the Web browser, type the following:
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You can avoid this problem using the headers_sent() function, which
checks whether or not data has been sent to the Web browser.
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Step 6
Dynamically determine the redirection URL and then call the header() function.
header ('Location: http://' . $_SERVER['HTTP_HOST'] .
dirname($_SERVER['PHP_SELF']) . '/newpage.php');
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Passing values
You can add name=value pairs to the URL in a header() call to pass
values to the target page. In this example, if you added this line to the
script, prior to redirection:
$url .= '?name=' . urlencode ("$fn $ln");
then the thanks.php page could greet the user by $_GET['name'].
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30. End
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