CSSE 290 Web Programming

Lecture 6: Intro to PHP

Reading: 5.1 - 5.2

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].

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5.1: Server-Side Basics

URLs and web servers

http://server/path/file

Server-Side web programming

php jsp ruby on rails asp.net django

What is PHP?

PHP logo

Lifecycle of a PHP web request

PHP server

Why PHP?

There are many other options for server-side languages: Ruby on Rails, JSP, ASP.NET, etc. Why choose PHP?

Hello, World!

The following contents could go into a file hello.php: 

<?php
print "Hello, world!";
?>
Hello, world!

Viewing PHP output

PHP local output PHP server output

5.2: PHP Basic Syntax

Console output: print 

print "text";

print "Hello, World!\n";
print "Escape \"chars\" are the SAME as in Java!\n";

print "You can have
line breaks in a string.";

print 'A string can use "single-quotes".  It\'s cool!';
Hello, World! Escape "chars" are the SAME as in Java! You can have line breaks in a string. A string can use "single-quotes". It's cool!

Arithmetic operators

Variables 

$name = expression;

$user_name = "PinkHeartLuvr78";
$age = 16;
$drinking_age = $age + 5;
$this_class_rocks = TRUE;

Types

Comments 

# single-line comment

// single-line comment

/*
multi-line comment
*/

for loop 

for (initialization; condition; update) {
	statements;
}

for ($i = 0; $i < 10; $i++) {
	print "$i squared is " . $i * $i . ".\n";
}

if/else statement

if (condition) {
	statements;
} elseif (condition) {
	statements;
} else {
	statements;
}

while loop (same as Java) 

while (condition) {
	statements;
}

do {
	statements;
} while (condition);

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

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

String type 

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

Interpreted strings

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

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"
NameJava 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
  • TRUE and FALSE keywords are case insensitive

Functions 

function name(parameterName, ..., parameterName) {
	statements;
}

function bmi($weight, $height) {
	$result = 703 * $weight / $height / $height;
	return $result;
}

Calling functions

name(expression, ..., expression);

$w = 163;  # pounds
$h = 70;   # inches
$my_bmi = bmi($w, $h);

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 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"

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>

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

Let's do an example together

PascalTriangle