Introduction to PHP –Part.1

8/7/2019 Introduction to PHP Part.1

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Introduction to PHPPart.1Chapter 9 from text book

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Outline

Server-Side Basics

PHP Basic Syntax

Data Types

Control Structures

Arrays

Embedded PHP

Advanced PHP Syntax

Functions

Variable Scope

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Do you want to build a website like:

3http://builtwith.com


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Server-Side Basics

some URLs actually specify programs that the web

server should run, and then send their output back toyou as the result: http://www.ksu.edu.sa/Pages/default.aspx

the above URL tells the server ksu.edu.sa to run the programdefault.aspx and send back its output

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BrowserPresentation

TierDatabase

Web Server

Logic Tier

Three-Tier
http://www.ksu.edu.sa/Pages/default.aspxhttp://www.ksu.edu.sa/Pages/default.aspx


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Server-Side Web Programming

Server-side pages are programs written usingone of many web programming languages/frameworks examples: PHP, Java/JSP, Ruby on Rails, ASP.NET,

Python, Perl

The web server contains software thatallows it to run those programs and sendback their output as responses to webrequests

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What is PHP?

PHP stands for "PHP HypertextPreprocessor"

A server-side scripting language

Used to make web pages dynamic: Provide different content depending on context

Interface with other services: database, e-mail, etc

Authenticate users

Process form information PHP code can be embedded in XHTML

code

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Lifecycle of a PHP web request

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Browser requests a .html file (static content): server just sends that file

Browser requests a .php file (dynamic content): server reads it, runs

any script code inside it, then sends result across the network

-script produces output that becomes the response sent back


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Hello, World!

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

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Hello, world!

A block or file of PHP code begins with

PHP statements, function declarations, etc. appear between theseendpoints


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Viewing PHP output

You can't view your .php page on your local hard drive; you'll either see

nothing or see the PHP source code

if you upload the file to a PHP-enabled web server, requesting the .php

file will run the program and send you back its output

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PHP Syntax Template

HTML content

HTML content

HTML content ...

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Any contents of a .php file between areexecuted as PHP code

All other contents are output as pure HTML

PHP statements are terminated with semicolons


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Console Output: print

print "Hello, World!\n";

print "Escape \"chars\" are the SAME as

in Java!\n";

print "You can have line breaks in a

string.";

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Syntax:print text;

Hello, World! Escape "chars" are the SAME as in Java! You can have line

breaks in a string.

Some PHP programmers use the equivalentecho instead of print


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Comments

// single-line comment

# single-line comment

/*

multi-line comment

*/

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Variables

Syntax:$name = expression;

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$user_name = Amal Ahmad";

$age = 13;

$College_age= $age + 5;

$this_class_is_useful= TRUE; Names are case sensitive; keywords and function names are not

case sensitive.

Names always begin with $, on both declaration and usage

Always implicitly declared by assignment (type is not written) A loosely typed language (like JavaScript)

A variable that has not been assigned a value is unbound and has

the value NULL

IsSet($x) function, checks if the variable $x is set to a value or

not.


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Types

Basic types: int, float, boolean, string, array, object, NULL

Type can be determined with the gettype function and

with the is_int function and similar functions for

other types

Type conversions can be forced in three ways

(int)$sum

intval($sum) using several conversion functions

settype($x, integer)

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Types

Implicit type conversions as demanded by thecontext in which an expression appears

A string is converted to an integer if a

numeric value is required and the string startswith a digit or a sign.

A string is converted to a double if a numeric

value is required and the string is a valid

double literal (including either a period or eor E)

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String Type

$favorite_color= Black";

print $favorite_color[2]; // a

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Zero-based indexing using bracket notation

There is no char type; each letter is itself a String String concatenation operator is . (period), not+

- 5 + "2 nice books" === 7

- 5 . "2 nice books " === "52 nice books "

Can be specified with " " or ' '


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Interpreted strings

$age = 16;

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

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

//You are 16 years old.

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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


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String functions

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bool (Boolean) Type

$feels_like_summer = TRUE;

$php_is_bad = FALSE;

$student_count = 217;

$nonzero = (bool) $student_count; // TRUE

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The following values are considered to be FALSE (all others

are TRUE):

- 0 and 0.0 (but NOT 0.00 or 0.000)

- "", "0", and NULL (includes unset variables)

- Arrays with 0 elements Can cast to booleanusing (bool)

FALSE prints as an empty string (no output); TRUE prints as 1 TRUE and FALSE keywords are case insensitive


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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

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Int for integers and float for reals

Division between two int values can produce a float


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Math operations

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the syntax for method calls, parameters,

returns is the same as Java


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Relational Operators

PHP has the usual comparison operators: >,


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Boolean Operators

PHP supports &&, || and ! as inC/C++/Java

The lower precedence version and and

or are provided The xor operator is also provided

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if/else Statement

if (condition) {

statements;

} elseif(condition) {

statements;

} else {

statements;

}

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NOTE: although elseif keyword is much more common,

else if is also supported


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for loop (same as Java)

for (initialization; condition; update) {

statements;

}

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for ($i = 0; $i < 10; $i++) {

print "$i squared is " . $i * $i . ".\n";

}


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while loop (same as Java)

while (condition) {

statements;

}

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do {

statements;

} while (condition);

break and continue keywords also behave as inJava


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Arrays

Arrays in PHP combine the characteristicsof regular arrays and hashes

An array can have elements indexed numerically.

These are maintained in order An array, even the same array, can have elements

indexed by string. These are not maintained in

any particular order

The elements of an array are, conceptually,

key/value pairs

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Array Creation

Two ways of creating an array $a = array(); // empty array (length 0)

Assigning a value to an element of an array,e.g. $a[0]=7; // one element

Create a numerically indexed array$list =array(23, xiv, bob, 777);

Create an array with string indexes $a = array(a =>apple, o =>orange)

Array elements are accessed by using a subscript insquare brackets.

To append, use bracket notation without specifying anindex

$a2 = array("some", "strings", "in", "an", "array");

$a2[] = "Ooh!"; // add string to end (at index 5)

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Array functions

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Functions for Dealing with Arrays

$cites = array(Makkah, Madeena, Riyadh,Khubar);

unset($cites[2]); // removes Riyadh

$x = array_keys($cities); // returns 0,1,3

$y = array_values($cities); // returns Makkah,

Madeena, Khubararray_key_exists(2, $cites); //returns false

$words = explode( ,This is a string); // returns

anarray consists of 4 elements This, is, a,

string

$str = implode( , $cites ); // returns a string

MakkahMadeenaKhubar

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Sequential Access to Array

Elements PHP maintains a marker in each array, called the current

pointer Several functions in PHP manipulate the current pointer

The pointer starts at the first element when the array is created

The next function moves the pointer to the nextelement and returns the value there

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$cites = array(Makkah, Madeena, Riyadh,

Khubar);

$city = current($cities);

print ($city - );

While ($city = next($cities))

print ($city - );

Makkah - Madeena - RiyadhKhubar-


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Sequential Access to Array Elements

The each function move the pointer to the nextelement and returns the key/value pair at the previousposition The key and value can be accessed using the keys key and

value on the key/value pair

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$cites = array(Makkah => 45, Madeena => 48,

Riyadh => 50, Khubar => 43);

While ($city = each($cities)){

$name = $city[key];

$temp = $city[value]

print (The temperature of $city is $temp
);}

The temperature of Makkah is 45

The temperature of Madeena is 48

The temperature of Riyadh is 50

The temperature of Khubar is 43


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Sequential Access to Array Elements

next and currentfunctions return false ifno more elements are available

prev moves the pointer back towards thebeginning of the array

reset moves the pointer to the beginning ofthe array

PHP provides the array_push function that

appends its arguments to a given array

The function array_pop removes the lastelement of a given array and returns it

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Iterating Through an Array

The foreach statement has two forms for iterating throughan array

foreach (arrayas scalar_variable) loopbody

foreach (arrayas key => value) loop body

The first version assigns each value in the array to thescalar_variable in turn

The second version assigns each key to key and theassociated value to value in turn

In this example, each day and temperature is printed

$lows = array("Mon" => 23, "Tue" => 18, "Wed"=> 27);

foreach ($lows as $day => $temp)

print("The low temperature on $day was $temp
");

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Embedding code in web pages

most PHP programs actually produce HTML astheir output

dynamic pages; responses to HTML form submissions;

etc.

an embedded PHP program is a file that

contains a mixture of HTML and PHP code

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Printing HTML tags in PHP = bad

style


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Functions

Function syntax:function name([parameters]) {...}

The parameters are optional, but not theparentheses

Function names are case insensitive A return statement causes the function to

immediately terminate and return a value, if any,provided in the return A function that reaches the end of the body

without executing a return, returns no value

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Parameters

A formal parameter, specified in a functiondeclaration, is simply a variable name If more actual parameters are supplied in a call than

there are formal parameters, the extra values areignored

If more formal parameters are specified than thereare actual parameters in a call then the extra formalparameters receive no value

PHP defaults to pass by value

Putting an ampersand & in front of a formal parameterspecifies that pass-by-reference

An ampersand can also be appended to the actualparameter (which must be a variable name)

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Variable scope

$Last_Name = ""; // global

...

function myFunc() {

global $Last_Name;

$first_Name= Norah"; // local

$Last_Name = $Last_Name $first_Name;

print " $Last_Name ";

}

Variables declared in a function are local to that function Variables not declared in a function are global

If a function wants to use a global variable, it must have a

global statement

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