PHP
By Web Monkey
Page 3 — Link Intelligently
--------------------------------------------------------------------------------
We're going to take that looping power we just learned and
use it in a more practical example. But before we proceed
here, you should know how to work with forms, the querystring,
and the GET and POST methods. Jay covered this not long ago,
so go take a look at his article if this is unfamiliar to
you.
Right now I'm going to work with the querystring. As you
should know, there are three ways to get information into
the querystring. The first is to use the GET method in a form.
The second is to type the information into the URL on your
browser. And third, you can embed a querystring in a standard
link. Just make the anchor tag look something like this: <a
href="http://my_machine/mypage.php3?id=1">. We're
going to use this technique right now.
First off, lets query our database again and list the employee
names. Look at the following script. Much of this should look
pretty familiar by now.
<html>
<body>
<?php
$db
= mysql_connect("localhost", "root");
mysql_select_db("mydb",$db);
$result
= mysql_query("SELECT * FROM employees",$db);
if
($myrow = mysql_fetch_array($result)) {
do
{
printf("<a
href=\"%s?id=%s\">%s %s</a><br>\n",
$PHP_SELF, $myrow["id"], $myrow["first"],
$myrow["last"]);
}
while ($myrow = mysql_fetch_array($result));
} else
{
echo
"Sorry, no records were found!";
}
?>
</body>
</html>
Everything's about the same except the printf function, so
let's look at it in some detail.
First notice that each quotation mark is preceeded by a backslash.
The backslash tells PHP to display the character following
it, rather than treat it as part of the code. Also note the
use of the variable $PHP_SELF. This variable, which stores
the script's name and location, is passed along with every
PHP page. It's helpful here because we just want this file
to call itself. Using $PHP_SELF, we can be sure that will
happen, even if the file is moved to another directory - or
even another machine.
As I just mentioned, these links will recall the page. On
the second time through, however, some information will be
added to the querystring.
PHP does a nifty thing when it sees a name=value pair in
the querystring. It automatically creates a variable with
the name and value the querystring indicated. This feature
allows us to test if it's the first or second time through
this page. All we have to do is ask PHP if the variable $id
exists.
Once I know the answer to that question, I can display a
different set of information the second time through. Here's
how:
<html>
<body>
<?php
$db
= mysql_connect("localhost", "root");
mysql_select_db("mydb",$db);
//
display individual record
if
($id) {
$result
= mysql_query("SELECT * FROM employees WHERE id=$id",$db);
$myrow
= mysql_fetch_array($result);
printf("First
name: %s\n<br>", $myrow["first"]);
printf("Last
name: %s\n<br>", $myrow["last"]);
printf("Address:
%s\n<br>", $myrow["address"]);
printf("Position:
%s\n<br>", $myrow["position"]);
} else
{
//
show employee list
$result
= mysql_query("SELECT * FROM employees",$db);
if
($myrow = mysql_fetch_array($result)) {
//
display list if there are records to display
do
{
printf("<a
href=\"%s?id=%s\">%s %s</a><br>\n",
$PHP_SELF, $myrow["id"], $myrow["first"],
$myrow["last"]);
}
while ($myrow = mysql_fetch_array($result));
}
else {
//
no records to display
echo
"Sorry, no records were found!";
}
}
?>
</body>
</html>
This code is getting complex now, so I've started to use comments
to keep track of what's going on. You can use // to make a
single-line comment or /* and */ to start and end a large
comment block.
And there we have it: your first truly useful PHP/MySQL script!
Now let's take a look at how to plug forms into it and send
information back into the database.
next page»
|
