Php

PHP Introduction

Mohamed Ashraf

PHP Hypertext Preprocessor

 No joke, that’s what it stands for
 Now very widely used for websites
 Only three years ago it was considered a
risky alternative for development
 Has a lot of community support

Simple PHP

 PHP is meant to be invoked inline with
content
 Page “escapes” into and out of a regular html
document
 File extension is .php (was .php3 for version
3)
 Initial use was control flow and simple
scripting

A quick example

 <html>
<head>Test page</head>
<body>
The time is now
<?php
echo date();
?>
<hr>
</body>
</html>

A quick example

 <html>
<body>
The time is now
<?php here we “jump into” php
echo date();
?> here we “jump” back out
<hr>
</body>
</html>

Another example
<?php
include “utilities.php”;
?>
<html>
<body>
<?php
if ($utils->isFriendly()) {
echo “The time is now “ . date();
} else {
echo “I will not give you the time of day”;
}
?>
<hr>
</body>
</html>

Another example – harder to read
<?php
include “utilities.php”;
?>
<html>
<body>
<?php
if ($utils->isFriendly()) {
echo “The time is now “ . date();
} else {
?>
<i>I will not give you the time of day!</i>
<?php
}
?>
<hr>
</body>
</html>

More PHP language details

 Variables are implicitly typed
 This is good
 This is bad
 Variables start with $
 All get/post variables automatically defined
 With most default server settings
 With an inline directive if need be

Defined variable example
 foo.html:
<html><head></head><body>
<form submit=“getFoo.php”>
Enter your name:
<input type=“text” name=“username”>
<input type=“submit”>
</body></html>
 getFoo.php:
<html><head></head></body>
Your name is
<?php
if (!strcmp($username)) {
echo $username;
} else {
echo “not given”;
}
?>
!<br>
</body></html>

Function list examples

 http://www.php.net/manual/en/function.strlen.
php
 All string functions
 Some are “obvious” to c programmers
 strlen, printf, fprintf, strpos
 Some are web tailored
 htmlentities, htmlspecialchars
 Others are new (hacky)
 addcslashes, explode, soundex, quotemeta, …

Classes

 OOP
 Class structures will be defined, helping
integration with other apps and work together
 APIs followed by implementation
 Inheritance
 Object serialization
 “Magic functions”

Class example
class Cart
{
var $items; // Items in our shopping cart
// Add $num articles of $artnr to the cart
function add_item ($artnr, $num)
{
$this->items[$artnr] += $num;
}
// Take $num articles of $artnr out of the cart
function remove_item ($artnr, $num)
{
if ($this->items[$artnr] > $num) {
$this->items[$artnr] -= $num;
return true;
} else {
return false;
}
}
}

Inheritance example
Class ParentObject {
var $value;
function ParentObject() {
$this->value = 42;
}
}
class MemberObject extends ParentObject {
var $string;
function MemberObject() {
$this->string = "This is a test string.";
$this->ParentObject();
}
}
class ObjTest {
var $ObjPointer;
function ObjTest() {
$tmp = new MemberObject;
$this->ObjPointer = $tmp;
}
}
$object = new ObjTest;
echo "String Contents: " . $object->ObjPointer->string . "n";
echo "Value Contents: " . $object->ObjPointer->value . "n";

Back to being hacky…

 “->” is NOT the same thing as it is in c++
 No pointers in PHP
 ONLY a member operator
 Oh, you wanted pointers?
 Variable variables
 Yeah, you heard right
 Don’t get me started…

Variable variables and classes example

class a {
var $b;
}

$object = new a;
$object->b = "hello";
$member_name = 'b';
echo $object->$member_name;
$object->$member_name = " world";
echo $object->$member_name;

Resources

 http://www.php.net
 http://www.w3schools.com

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