CSSE 290 Web Programming

Lecture 7: Embedded PHP

Reading: 5.3 - 5.5

Except where otherwise noted, the contents of this document are Copyright 2012 Marty Stepp, Jessica Miller, and Victoria Kirst. All rights reserved. Any redistribution, reproduction, transmission, or storage of part or all of the contents in any form is prohibited without the author's expressed written permission.

Otherwise note: Claude Anderson was given permission to modify the slides for CSSE 290 at Rose-Hulman by author Jessica Miller. The authors' original slides, based on Web Programming Step by Step, can be seen at http://webstepbook.com.

Some of the examples in some days' slides are from David Fisher at Rose-Hulman, who was kind enough to allow me to use them. My intention is to mark these examples with [DSF].

5.2: PHP Basic Syntax

5.1: Server-Side Basics
5.2: PHP Basic Syntax
5.3: Embedded PHP
5.4: Advanced PHP Syntax

PHP syntax template

HTML content

	<?php
	PHP code
	?>

HTML content

	<?php
	PHP code
	?>

HTML content ...

any contents of a .php file between <?php and ?> are executed as PHP code
all other contents are output as pure HTML
can switch back and forth between HTML and PHP "modes"

Math operations

$a = 3;
$b = 4;
$c = sqrt(pow($a, 2) + pow($b, 2));

math functions
`abs`	`ceil`	`cos`	`floor`	`log`	`log10`	`max`
`min`	`pow`	`rand`	`round`	`sin`	`sqrt`	`tan`

math constants
`M_PI`	`M_E`	`M_LN2`

the syntax for method calls, parameters, returns is the same as Java

`int` and `float` types

$a = 7 / 2;               # float: 3.5
$b = (int) $a;            # int: 3
$c = round($a);           # float: 4.0
$d = "123";               # string: "123"
$e = (int) $d;            # int: 123

int for integers and float for reals
division between two int values can produce a float

`String` type

$favorite_food = "Ethiopian";
print $favorite_food[2];            # h

zero-based indexing using bracket notation
string concatenation operator is . (period), not +
- 5 + "2 turtle doves" produces 7
- 5 . "2 turtle doves" produces "52 turtle doves"
can be specified with "" or ''

Interpreted strings

$age = 16;
print "You are " . $age . " years old.\n";
print "You are $age years old.\n";    # You are 16 years old.

strings inside " " are interpreted
- variables that appear inside them will have their values inserted into the string

strings inside ' ' are not interpreted:

print 'You are $age years old.\n';    # You are $age years old.\n

if necessary to avoid ambiguity, can enclose variable in {}:

print "Today is your $ageth birthday.\n";     # $ageth not found
print "Today is your {$age}th birthday.\n";

`String` functions

# index  0123456789012345
$name = "Stefanie Hatcher";
$length = strlen($name);              # 16
$cmp = strcmp($name, "Brian Le");     # > 0
$index = strpos($name, "e");          # 2
$first = substr($name, 9, 5);         # "Hatch"
$name = strtoupper($name);            # "STEFANIE HATCHER"

Name	Java Equivalent
`strlen`	`length`
`strpos`	`indexOf`
`substr`	`substring`
`strtolower`, `strtoupper`	`toLowerCase`, `toUpperCase`
`trim`	`trim`
`explode`, `implode`	`split`, `join`
`strcmp`	`compareTo`

bool (Boolean) type

$feels_like_summer = FALSE;
$php_is_rad = TRUE;

$student_count = 217;
$nonzero = (bool) $student_count;     # TRUE

the following values are considered to be FALSE (all others are TRUE):
- 0 and 0.0
- "", "0", and NULL (includes unset variables)
- arrays with 0 elements
can cast to boolean using (bool)
FALSE prints as an empty string (no output); TRUE prints as a 1

TRUE and FALSE keywords are case insensitive

5.3: Embedded PHP

5.1: Server-Side Basics
5.2: PHP Basic Syntax
5.3: Embedded PHP
5.4: Advanced PHP Syntax

Printing HTML tags in PHP = bad style

<?php
print "<!DOCTYPE html>\n";
print "<html>\n";
print "  <head>\n";
print "    <title>Geneva's web page</title>\n";
...
for ($i = 1; $i <= 10; $i++) {
	print "<p class=\"count\"> I can count to $i! </p>\n";
}
?>

printing HTML tags with print statements is bad style and error-prone:
- must quote the HTML and escape special characters, e.g. \"
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: evaluates and embeds an expression's value into HTML
<?= expr ?> is equivalent to <?php print expr; ?>

Expression block example

<!DOCTYPE html>
<html>
	<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>

Common errors: unclosed braces, missing = sign

	<body>
		<p>Watch how high I can count:
			<?php for ($i = 1; $i <= 10; $i++) { ?>
				<? $i ?>
		</p>
	</body>
</html>

</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'
if you forget = in <?=, the expression 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>

This is a level 1 heading.

This is a level 2 heading.

This is a level 3 heading.

expression blocks can even go inside HTML tags and attributes

CSSE 290 Web Programming

Session 7: Embedded PHP

CSSE 290 Web Programming

Lecture 7: Embedded PHP

Reading: 5.3 - 5.5

5.2: PHP Basic Syntax

PHP syntax template

Math operations

int and float types

String type

Interpreted strings

String functions

bool (Boolean) type

5.3: Embedded PHP

Printing HTML tags in PHP = bad style

PHP expression blocks

The answer is 42

Expression block example

Common errors: unclosed braces, missing = sign

Complex expression blocks

This is a level 1 heading.

This is a level 2 heading.

This is a level 3 heading.

`int` and `float` types

`String` type

`String` functions