Spring Semester 2003
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Spring Semester 2003 |
Last week most everybody managed to install PHP4 as an Apache module.
We're also finished with
mysql. We'll also frequently refer back to compare PHP with what we've done thus far.
Today we start PHP, and we use this set of notes as the start of an introduction to PHP.
As a reminder I include here my crontab file:
One should do this when one is completely convinced the setup is perfect.burrowww.cs.indiana.edu% crontab -l 0 8 * * * /u/dgerman/apache/apache_1.3.26/bin/apachectl graceful > /dev/null burrowww.cs.indiana.edu%
Otherwise we need to delete the accumulated e-mail on a daily basis.
PHP (What's in a name?)
PHP originally meant Personal Home Page.
Later following the GNU's recursive play on words (Gnu is Not Unix) the acronym changed.
So it now stands for PHP a Hypertext Processor.
Whatever it stands for, though, it will simplify your life somewhat.
Your PHP files will be placed under htdocs.
The simplest PHP file has no PHP inside per se.
We need to describe how this goes, but let's keep going for now.burrowww.cs.indiana.edu% pwd /nfs/paca/home/user1/dgerman/apache/apache_1.3.26/htdocs/weekSix burrowww.cs.indiana.edu% ls -ld one* -rw-r--r-- 1 dgerman faculty 120 Feb 14 12:07 one.php burrowww.cs.indiana.edu% cat one.php <html> <head><title>PHP Scripts</title></head> <body bgcolor=white> <h1> Hello, world! </h1> </body> </html> burrowww.cs.indiana.edu%
PHP is a programming language, so it has variables, assignment statements, expressions, etc.
It will resemble Perl to a certain extent.
But let's see some (more) examples first.
Here's a second example.
Here's the source code:
(I placed it in<html>
<head><title>PHP Scripts</title></head>
<body bgcolor=white>
<h1> Hello, world! </h1>
<? $i = 1; ?>
I have set <code>$i</code> to 1, but you can't see it. <p>
Here's the value: <? echo $i; ?> <p>
Hope you can see it now. <p>
<? $i = $i + 1; ?>
Now <code>$i</code> is <?=$i?>. <p>
</body>
</html>
two.php, since
one.php already looks like
this). I don't even need to post the source code here.
Copy the file two.php into two.phps and
access it.
Better yet, create a symbolic link from two.phps to
two.php as follows:
PHP knows how to process both actual PHP code and PHP listing source code.ln -s two.php two.phps
There are three different types of PHP tags, but we will use
this one (<?, ?>) for now.
One important thing is that variables in HTML forms are easier to name.
For example, let's start from this form (call it orderForm.php):
<html><head><title>Bob's Auto Parts</title></head><body bgcolor="white">
<h1>Bob's Auto Parts</h1>
<h3> Order Form</h3>
<form action="processOrder.php" method="post">
<table border=0>
<tr bgcolor="#cccccc">
<td width=150> Item </td>
<td width=15>Quantity</td>
</tr>
<tr>
<td>Tires</td>
<td align=center><input type="text" name="tireqty" size=3 maxlength=3></td>
</tr>
<tr>
<td>Oil</td>
<td align=center><input type="text" name="oilqty" size=3 maxlength=3></td>
</tr>
<tr>
<td>Spark Plugs</td>
<td align=center><input type="text" name="sparkqty" size=3 maxlength=3></td>
</tr>
<tr>
<td colspan=2
align=center><input type="submit" value="Submit Order"></td>
</tr>
</table>
</form>
</body>
</html>(That could also be a CGI script, but we want to use PHP now).
As a matter of fact, can you describe the output (format and contents)?
Great!
Now the simplification.
First, we write this (call it processOrder.php):
<html><head><title>Order Results</title></head><body bgcolor="white">
<h1> Bob's Auto Parts</h1>
<h3>Order Results</h3>
<?
echo "Thank you for your order!";
?>
</body>
</html>I hope that looks good to you.
Let's enhance processOrder.php a bit.
<html><head><title>Order Results</title></head><body bgcolor="white">
<h1> Bob's Auto Parts</h1>
<h3>Order Results</h3>
<?
$tireqty += 0;
$oilqty += 0;
$sparkqty += 0;
echo $tireqty . " tires <br>" .
$oilqty . " bottles of oil <br>" .
$sparkqty . " spark plugs <p>" ;
if ($tireqty >= 0 &&
$oilqty >= 0 &&
$sparkqty >= 0 &&
($tireqty + $oilqty + $sparkqty > 0) ) {
echo "Thank you for your order!";
} else {
echo "This is not a valid order. ";
}
?>
</body>
</html>Please note the names of the variables and the names of the form elements.
Here's the source code for the new processOrder:
<html><head><title>Order Results</title></head><body bgcolor="white">
<h1> Bob's Auto Parts</h1>
<h3>Order Results</h3>
<?
$tireqty += 0;
$oilqty += 0;
$sparkqty += 0;
echo $tireqty . " tires <br>" .
$oilqty . " bottles of oil <br>" .
$sparkqty . " spark plugs <p>" ;
if ($tireqty >= 0 &&
$oilqty >= 0 &&
$sparkqty >= 0 &&
($tireqty + $oilqty + $sparkqty > 0) ) {
echo "Thank you for your order!";
} else {
echo "This is not a valid order. ";
}
?>
</body>
</html>
The elements of %ENV are available by their short names, too:
<html><head><title>This is my portfolio</title></head><body bgcolor=white>
<? echo $QUERY_STRING ?> <p>
<table width=100% cellpadding=2>
<tr> <td align=center>
<? if ($QUERY_STRING == "seven") {
echo "Lindley 07";
} else {
echo "<a href=\"$SCRIPT_NAME?seven\">Lindley 07</a>";
}
?>
</td> <td align=center>
Lindley 08
</td> <td align=center>
Lindley 01
</td> <td align=center>
Lindley 09
</td>
</tr>
<tr> <td colspan=4 align=center>
<? if ($QUERY_STRING == "seven") {
echo
"<img src=\"http://www.cs.indiana.edu" .
"/dept/img/lh07.gif\">";
} else {
echo
"<img src=\"http://www.cs.indiana.edu" .
"/l/www/classes/a202-dger/sum99/a202.gif\">";
}
?>
</td>
</tr>
</table>
</table>
</body>
</html>
<html><head><title>This is my portfolio</title></head><body bgcolor=white>
<? echo $QUERY_STRING ?> <p>
<table width=100% cellpadding=2>
<tr> <td align=center>
<? if ($QUERY_STRING == "seven") {
echo "Lindley 07";
} else {
echo "<a href=\"$SCRIPT_NAME?seven\">Lindley 07</a>";
}
?>
</td> <td align=center>
Lindley 08
</td> <td align=center>
Lindley 01
</td> <td align=center>
Lindley 09
</td>
</tr>
<tr> <td colspan=4 align=center>
<? if ($QUERY_STRING == "seven") {
echo
"<img src=\"http://www.cs.indiana.edu" .
"/dept/img/lh07.gif\">";
} else {
echo
"<img src=\"http://www.cs.indiana.edu" .
"/l/www/classes/a202-dger/sum99/a202.gif\">";
}
?>
</td>
</tr>
</table>
</table>
</body>
</html>
What does this bring to mind?
The calculator likely becomes easier to write also:
<html><head><title>Bank Accounts</title></head><body bgcolor="white">
<? if ($fun == "add") {
$acc += $arg;
} else if ($fun == "sub") {
$acc -= $arg;
} else {
}
?>
Current accumulator is: <? echo $acc ?>
<form method="post" action="<? echo $SCRIPT_NAME; ?>">
Amount: <input type="text" name="arg"> <p>
Action: <select name="fun">
<option value="non"> Click Me!
<option value="add"> Deposit
<option value="sub"> Withdraw
</select> <p>
<input type="hidden" name="acc" value="<? echo $acc; ?>">
Fill in the form then push: <input type="submit" value="Proceed">
</form>
</body></html>hidden field by now. It helps us keep state on the client side.
PHP provides the ability to manage state on the server side.
Here's a typical script.
<? session_start();
if (session_is_registered("acc")) {
if ($fun == "add") $acc += $arg;
else if ($fun == "sub") $acc -= $arg;
} else {
$acc = 0;
session_register("acc");
}
?>
<html>
<head>
<title>Sessions Examples</title>
</head>
<body bgcolor=white>
<form method="POST" action="<? echo $SCRIPT_NAME; ?>">
The current value of the accumulator is: <? echo $acc ?> <p>
<table cellpadding=2>
<tr>
<td> Amount: </td>
<td> <input type="text" name="arg" size=4> </td>
<td> Function: </td>
<td> <select name="fun">
<option value="non"> Click Me!
<option value="add"> Deposit
<option value="sub"> Withdraw
</select>
</td>
</tr>
</table>
<p> Enter the amount, select a function, then press
<input type="submit" value="Proceed"> <p>
</form>
</body>
</html>/tmp if I work with this calculator a bit (which
is what the example wants to bring forth):
My accumulator was 122 at the time I printed the file.burrowww.cs.indiana.edu% ls -ld /tmp/sess_05e56a5ed8be5e3a0ef771d9fb582df9 -rw------- 1 dgerman faculty 10 Oct 17 14:44 /tmp/sess_05e56a5ed8be5e3a0ef771d9fb582df9 burrowww.cs.indiana.edu% cat /tmp/sess_05e56a5ed8be5e3a0ef771d9fb582df9 acc|i:122;burrowww.cs.indiana.edu% burrowww.cs.indiana.edu%
The name of the file contains the random session ID (in blue).
The contents of the file contains the server-side state (environment).
That is in red.
Note that for every browser that calls, a session ID is created.
The session ID is sent to the browser, and kept in a cookie, there.
(Other ways of storing the session ID on the browser are possible, too).
A file with the ownership of the server will then be created on the server.
Where will it be created?
Your config file (php.ini) determines
that, and here's the line in it.
To summarize:ifx.nullformat = 0 [Session] ; Handler used to store/retrieve data. session.save_handler = files ; Argument passed to save_handler. In the case of files, this is the path ; where data files are stored. session.save_path = /tmp ; Whether to use cookies. session.use_cookies = 1 ; Name of the session (used as cookie name). session.name = PHPSESSID ; Initialize session on request startup. session.auto_start = 0
session_start()
checks to see if an ID is submitted by the browser with the request, and if that ID is already available on the server.
a new one will be generated, and will be sent to the browser. This is the beginning of a new session. The browser has to keep it and submit it with every new request.
then we know
who we are talking to, so we refer to the corresponding
file in the session.save_path directory.
session_register(varName)
is used to associate variable names with values. These are stored under the appropriate session ID file on the server side (see my example above). They are retrieved from that file during subsequent calls in the same session (that is, for the same session ID).
session_is_registered(varName)
is used to check if a variable is registered already or not (that is, if it's stored on the server side in the file for this session ID).
session_unregister(varName)
is used to delete a variable from the file on the server associated with the session in which this instruction is run.
session_destroy()
deletes the session, that is, the file.
Next time we will cover:
At this point Homework Three should present no problem for you.