Introduction to PHP - Lecture - PHP - Prof G H Haldar, Lecture notes of Programming Languages

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PHP

What is PHP?



PHP stands for P HP: H ypertext P reprocessor

 PHP is a server-side scripting language, like ASP

 PHP scripts are executed on the server

 PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid,

PostgreSQL, Generic ODBC, etc.)

 PHP is an open source software (OSS)

 PHP is free to download and use

What do You Need?

 Download PHP

 Download PHP for free here: http://www.php.net/downloads.php

 Download MySQL Database

 Download MySQL for free here:

http://www.mysql.com/downloads/index.html

 Download Apache Server

 Download Apache for free here: http://httpd.apache.org/download.cgi

PHP Syntax

 Basic PHP Syntax



 A PHP file normally contains HTML tags, just like an HTML file, and

some PHP scripting code.

 Comments in PHP

 // ----to make a single-line comment or

 /* */ --- multiple lines

PHP Variables

 All variables in PHP start with a $ sign symbol.

$var_name = value;

 variable does not need to be declared before being set

 declared automatically when you use it

 Variable Naming Rules

 A variable name must start with a letter or an underscore "_"

 A variable name can only contain alpha-numeric characters and

underscores (a-Z, 0-9, and _ )

 A variable name should not contain spaces (use underscore)

Strings in PHP

 used for values that contains character strings

 The Concatenation Operator (.)

 concatenate two variables together

 strlen() function

 used to find the length of a string



 strpos() function

 used to search for a string or character within a string

 echo strpos("Hello world!","world");

Strings in PHP  (^) http://www.w3schools.com/php/php_ref_string.asp

PHP Operators

PHP constant

 like a variable,

 is a temporary placeholder in memory that holds a value.

 Unlike variables, the value of a constant never changes.

 PHP constants unlike variables do not begin with the "$" sign.

 When a constant is declared, the define() function is used and requires the name of the

constant and the value you want to give the constant

 Constants can be assigned the following types of data:

Integers - whole numbers or numbers without decimals.

Floating-point numbers (also known as floats or doubles) -

Strings - text or numeric information.

PHP constant

 define("STRING_CONSTANT", "This is my string.");

define("NUMERIC_CONSTANT", 5);

Flow Control Statements

 Conditional Statements

1. "if ... elseif ... else" statements.

if ( condition )

code to be executed if condition is true;

else code to be executed if condition is false;

2. "switch ... case ... default" statements.

 If you want to select one of many blocks of code to be executed, use the Switch

statement.

 The switch statement is used to avoid long blocks of if..elseif..else code.

 After a code is executed, break is used to stop the code from running into the

next case

Flow Control Statements

 Looping

 while - loops through a block of code if and as long as a specified condition

is true

 do...while - loops through a block of code once, and then repeats the loop as

long as a special condition is true. will execute a block of code at least once

 for - loops through a block of code a specified number of times

 foreach - loops through a block of code for each element in an array

foreach ( array as value ) { code to be executed; }

PHP Arrays

2. Associative Arrays

 each ID key is associated with a value.

 we can use the values as keys and assign values to them

 E.g. 1

 $ages = array("Peter"=>32, "Quagmire"=>30, "Joe"=>34);

 E.g. 2

$ages['Peter'] = "32";

$ages['Quagmire'] = "30";

$ages['Joe'] = "34";

PHP Arrays

3. Multidimensional Arrays

 (^) each element in the main array can also be an array.  (^) And each element in the sub-array can be an array, and so on.  (^) E.g. in practical