Lecture - Introduction to PHP

8/12/2019 Lecture - Introduction to PHP

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Web Development: Dynamically

Generated Content

Introduction to PHP


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PHP Start and End Tags

You need to inform the PHP engine that you want toexecute PHP code

You can do this using special tags to mark start andend of PHP code


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PHP Start and End Tags

Tag Style Start Tag End Tag

Standard tags

Short tags

ASP tags

Script tags

Standard and the script tags cab beguaranteed to work on any configuration


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The echoStatement and print() Function

The echostatement and the print() function areused to output data

Example

OR


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Combining HTML and PHP

A PHP script including HTML


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Adding Comments

Comments make it easier for other programmers to workwith your code

There two types of comments in PHP: Single-line comments which begin with // or #

//This is a single-line comment# This is also a single-line comment

Multi-line comments with /* and ending with */

/*This is a comment

and will be ignored by

PHP engine */


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PHP LANGUAGE STRUCTURE


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Variables

A variable consists of a name of your choosingpreceded by a $ sign

Variable names can include letters, numbers and theunderscore character but can not include spaces

A semi-colon is used to end a PHP statement$name_of_student;

$number123;

Variable names are case sensitive that means $sumand $Sum are treated as entirely different variablenames


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Variables

PHP is a loosely typed language This means that variable does not need to be

declared before adding a value to it.

PHP automatically converts the variable to the

correct data type, depending on its value


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Globals and Superglobals

PHP has predefined variables called superglobals These variables are always present and their values

are available to all your scripts


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Examples of Superglobals

$_GETcontains any variables provided to a scriptthrough the GET method

$_POSTcontains any variables provided to ascript through the POST method

$_COOKIE contains any variables provided to ascript through a cookie

$_FILES contains any variables provided to a scriptthrough file uploads


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Examples of Superglobals

$_SERVER contains information such as headers,file paths, and script locations

$_ENV contains any variables provided to a script aspart of the server environment

$_REQUEST contains any variables provided to ascript through any user input mechanism

$_SESSION contains any variables that arecurrently registered in a session


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Working with Strings

A string is a collection of characters, numbers, lettersenclosed in quotes

For example Interactive Media

Dynamic Websites

To make a string assign it a variable name$name=Jimmy

To create a srting you can use single or double quotes

A string can be printed using echo() or print()echo $name

Or

echo HND Interactive Media


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Concatenating Strings

To append a string at the end of another you can usethe concatenation operator which is the period(.)

$first_name=Jack;

$last_name=Murray;$full_name= $first_name. $last_name;


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String Functions

PHP has several functions to manipulatetext(Strings)

You would usually pass a variable by putting it inparentheses

The functions can return a value in addition toperforming tasks

Functions do not start with a dollar sign and areimmediately followed by parentheses


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String Functions strlen()

The function strlen()returns the length of a string


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String Functions htmlspecialchars()

The function htmlspecialchars()takes a string andthen converts special characters like >, to HTMLcode


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String Functions ucfirst()

The function ucfirst()changes the first character touppercase


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String Functions ucwords()

The function ucwords()changes the first characterof each word to uppercase


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String Functions trim()

The function trim()removes blank space from thebeginning and end of string


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String Functions strtoupper()

The function strtoupper()converts any lowercaseletters to uppercase


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PHP Data Types

Type Description

Boolean One of the values true or false

Integer A whole number

Float or Double A floating point number

String A collection of characters

Array An ordered set of valuesResource Reference to a third party resource e.g. database

NULL An uninitialized variable


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Operators and Expressions

Operators are symbols used to manipulate data A value that is operated on by operator is called

operand

A combination of operands and operators is called

expressions


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Assignment Operators

The assignment operator is =

$name=Dougie;

$sum=45;


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Working with Numbers

PHP has both integer and floating-point(decimal)number types

Number values are never enclosed within quotes

All numbers are presumed positive unless preceded

by a minus(-)


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Working with Numbers

Along with arithmetic operators you can use built-in

functions to manipulate numbers e.g. number_format() used to display numbers with specified

number of decimal places number_format()has the following syntax

number_format(variable, number of decimal places)

number_format($total, 3);

round() is used to decimal numbers to nearest whole number

round() has the following syntaxround(variable) e.g.

round($total);


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Arithmetic Operators

Operator Name

+ Addition

- Subtraction

/ Division

* Multiplication

% Modulus


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Combined Assignment Operators

Operator Example Equivalent to

+= $x+=5 $x=$x+5

-= $x-=5 $x=$x-5

/= $x/=5 $x=$x/5

*= $x*=5 $x=$x*5

%= $x%=5 $x=$x%5.= $x.= test $x=$x. test


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Automatically Incrementing and

Decrementing

A variable can be incremented by one as follows

$x=$x+1;

OR

$x+=1;


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Automatically Incrementing and

Decrementing

A variable can be decreased by 1 as follows:

$x=$x-1;

OR

$x-=1;

OR

$x--;


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Comparison Operators

Operator Name

== Equivalence

!= Non-equivalence

=== Identical

> Greater than

>= Greater than or equal to< Less than


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Constants

A constant is a value that does not change

A constant is defined using function define()

define (name_of_constant,41);


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Single vs Double Quotes

In PHP values enclosed within single quotes will be

treated literally whereas those within double quotes willbe interpreted

Lets say you have

echo $test_var=Some Text;

echo var is equal to $test_var; will print:

var is equal to Some Text

Whereas echo var is equal to $var; will print

var is equal to $test_var


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Special Characters

The following characters have special meaning whenenclosed in double quotes

Code Meaning

\ Double quotes

\ Single quotes\\ Backslash

\n New line

\r Carriage return

\t Tab\$ Dollar sign

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Lecture - Introduction to PHP

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