Embedded PHP
CSE 190 M (Web Programming), Spring 2008
University of Washington
Except where otherwise noted, the contents of this presentation are © Copyright 2008 Marty Stepp and Jessica Miller and are licensed under the Creative Commons Attribution 2.5 License.
Web services vs. embedded PHP
- the PHP programs we've written so far were web services (their output is plain text)
- most PHP programs actually produce HTML as their output
- example: responses to HTML form submissions
- an embedded PHP program is a file that contains a mixture of HTML and PHP code
A bad way to produce HTML in PHP
<?php
print "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.1//EN\"\n";
print " \"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd\">\n";
print "<html xmlns=\"http://www.w3.org/1999/xhtml\">\n";
print " <head>\n";
print " <title>My web page</title>\n";
...
?>
- printing HTML code with
print statements is ugly and error-prone:
- must quote the HTML and escape special characters, e.g.
\"
- must insert manual
\n line breaks after each line
- don't
print HTML; it's bad style!
Syntax for embedded PHP
html content
<?php
PHP code
?>
html content
- any contents of a
.php file that are not between <?php and ?> are output as pure HTML
- can switch back and forth between HTML and PHP "modes"
Embedded PHP example
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title>CSE 190 M: Embedded PHP</title></head>
<body>
<h1>Geneva's Counting Page</h1>
<p>Watch how high I can count:
<?php
for ($i = 1; $i <= 10; $i++) {
print "$i\n";
}
?>
</p>
</body>
</html>
- the above code would be saved into a file such as
count.php
- How many lines of numbers will appear? (View Source!)
Embedded PHP as form response
...
<body>
<h1>New account created.</h1>
<p>
<?php
$name = $_REQUEST["name"];
$email = $_REQUEST["email"];
...
print "\"Thank you\", $name, for creating an account with $email.\n";
?>
</p>
</body>
- users expect an HTML response page when they submit forms
- embedded PHP allows you run some server-side code and also send back an HTML response page
Practice problem: Photo gallery
Write an embedded PHP page that displays a gallery of photos. The page will show all images in the food_images subfolder of the script's directory on the server as thumbnails (each image uses the galleryimage style class so it will appear 150px tall). Clicking on any image should show that image at full size.
(solution,
source)
Embedded PHP + print = bad
...
<body>
<h1>Geneva's Counting Page</h1>
<p>Watch how high I can count:
<?php
for ($i = 1; $i <= 10; $i++) {
print "$i\n";
}
?>
</p>
</body>
- best PHP style is to use as few
print/echo statements as possible in embedded PHP code
- but without
print, how do we insert dynamic content into the page?
PHP expression blocks
<?= expression ?>
<h2>The answer is <?= 6 * 7 ?></h2>
The answer is 42
- PHP expression block: a small piece of PHP that evaluates and embeds an expression's value into HTML
Expression block example 1
<?php
$name = $_REQUEST["name"];
$email = $_REQUEST["emailaddress"];
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title>Account Creation</title></head>
<body>
<h1>New account created.</h1>
<p>
Thank you, "<?= $name ?>", for creating an
account with <?= $email ?>.
</p>
</body>
</html>
- expression blocks get rid of
print statement in previous example
- can often move PHP code up, out of the middle of the HTML
Expression block example 2
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title>CSE 190 M: Embedded PHP</title></head>
<body>
<?php
for ($i = 99; $i >= 1; $i--) {
?>
<p>
<?= $i ?> bottles of beer on the wall, <br />
<?= $i ?> bottles of beer. <br />
Take one down, pass it around, <br />
<?= $i - 1 ?> bottles of beer on the wall.</p>
<?php
}
?>
</body>
</html>
- this code could go into a file named
beer.php
Common error: unclosed braces
...
<body>
<p>Watch how high I can count:
<?php
for ($i = 1; $i <= 10; $i++) {
?>
<?= $i ?>
</p>
</body>
</html>
- if you open a
{ brace, you must have a matching } brace later (in the same PHP-mode block or a later one)
</body> and </html> above are inside the for loop, which is never closed
- if you forget to close your braces, you'll see an error about 'unexpected
$end'
Common error fixed
...
<body>
<p>Watch how high I can count:
<?php
for ($i = 1; $i <= 10; $i++) {
?>
<?= $i ?>
<?php
}
?>
</p>
</body>
</html>
Common error: Missing = sign
...
<body>
<p>Watch how high I can count:
<?php
for ($i = 1; $i <= 10; $i++) {
?>
<? $i ?>
<?php
}
?>
</p>
</body>
</html>
- a block between
<? ... ?> is often interpreted as the same as one between <?php ... ?>
- PHP evaluates the code, but
$i does not produce any output
Complex expression blocks
...
<body>
<?php
for ($i = 1; $i <= 3; $i++) {
?>
<h<?= $i ?>>This is a level <?= $i ?> heading.</h<?= $i ?>>
<?php
}
?>
</body>
<body>
<h1>This is a level 1 heading.</h1>
<h2>This is a level 2 heading.</h2>
<h3>This is a level 3 heading.</h3>
</body>
- expression blocks can even go inside HTML tags and attributes
Practice problem: Improved gallery
Update the photo gallery page's code to use PHP expression blocks. The code should not contain any print statements.
If you have time, add the ability for the user to upload a new image to the gallery. Have the gallery submit its POST data to itself.
(solution,
source)
