php - datatype,variable,constant,operators,array,include and require

PHP BASICS

DataType Variable Constant Operators Control and Looping structure Arrays PHP Errors Include vs Require

Bywww.Creativedev.in

DATATYPE

A Data type refer to the type of data a variable can store. A Data type is determined at runtime by PHP. If you assign a string to a variable, it becomes a string variable and if you assign an integer value, the variable becomes an integer variable.

CONTINUE...

PHP supports eight primitive types:

Four scalar types:

1. Boolean2. integer3. float (floating-point number, aka double)4. string

Two compound types:

5. array6. object

And finally three special types:

7. resource8. NULL9. callable

CONTINUE...

Integer : used to specify numeric valueSYNTAX:

<?php $variable = 10; ?>

Float : used to specify real numbersSYNTAX:

<?php

$variable = -10;

$variable1 = -10.5;

?>

Boolean: values true or false, also 0 or empty.SYNTAX:

<?php $variable = true; ?>

CONTINUE...

String: sequence of characters included in a single or double quote.

SYNTAX:

<?php

$string = 'Hello World';

$string1 = "Hello\n World";

?>

VARIABLE

Variables are used for storing a values, like text strings, numbers or arrays.

All variables in PHP start with a $ symbol.

SYNTAX:

$var_name = value;

Example:

$name = 'Bhumi';

VARIABLE SCOPE

Scope can be defined as the range of availability a variable has to the program in which it is declared. PHP variables can be one of four scope types:

1) Local variables

2) Function parameters

3) Global variables

4) Static variables

VARIABLE NAMING RULES

1) A variable name must start with a letter or an underscore "_". Ex, $1var_name is not valid.

2) Variable names are case sensitive; this means $var_name is different from $VAR_NAME.

3) A variable name should not contain spaces. If a variable name is more than one word, it should be separated with underscore. Ex, $var name is not valid,use $var_name

VARIABLE VARIABLES

Variable variables allow you to access the contents of a variable without knowing its name directly - it is like indirectly referring to a variable

EXAMPLE:

$a = 'hello';

$$a = 'world';

echo "$a $hello";

VARIABLE TYPE CASTING

Type casting is converting a variable or value into a desired data type. This is very useful when performing arithmetic computations that require variables to be of the same data type. Type casting in PHP is done by the interpreter.

PHP also allows you to cast the data type. This is known as Explicit casting. The code below demonstrates explicit type casting.

VARIABLE TYPE CASTING EXAMPLE

<?php

$a = 1;

$b = 1.5;

$c = $a + $b;

$c = $a + (int) $b;

echo $c;

?>

CONSTANTS

A constant is an identifier (name) for an unchangable value.

A valid constant name starts with a letter or underscore (no $ sign before the constant name).

Note: Unlike variables, constants are automatically global across the entire application.Constants are usually In UPPERCASE.

SYNTAX:

define(name, value, case-insensitive)

Parameters:name: Specifies the name of the constantvalue: Specifies the value of the constantcase-insensitive: Specifies whether the constant name should be case-insensitive.

Default is false

CONSTANT EXAMPLES

<?php

define('NAME','Bhumi');

echo NAME;

?>

PHP OPERATORS

1. Arithmetic Operators

OPERATOR DESCRIPTION EXAMPLE RESULT

+ Addition x=2,x+2 4

- Subtraction x=2,5-x 3

* Multiplication x=4,x*5 20

/ Division 15/5,5/2 32.5

% Modulus(division remainder)

5%2,10%8 12

++ Increment x=5,x++ 6

-- Decrement x=5,x-- 4

PHP OPERATORS

2. Assignment Operators

OPERATOR EXAMPLE IS THE SAME AS

= x=y x=y

+= x+=y x=x+y

-= x-=y x=x-y

*= x*=y x=x*y

/= x/=y x=x/y

.= x.=y x=x.y

%= X%=y x=x%y

PHP OPERATORS...

3. Logical Operators

OPERATOR DESCRIPTION EXAMPLE

&& and x=6,y=3(x < 10 && y > 1) return true

|| OR x=6,y=3(x==5 || y==5) return false

! not x=6,y=3!(x==y)return true

PHP OPERATORS

4. Comparison Operators

OPERATOR DESCRIPTION EXAMPLE

== is equal to 5==8 return false

!= is not equal 5!=8 return true

<> is not equal 5<>8 return true

> is greater than 5>8 return false

< is less than 5<8 return true

>= is greater than or equal to

5>=8 return false

<= is less than or equal to 5<=8 return true

CONTINUE...

5. Ternary Operator

? is represent the ternary operator

SYNTAX:

(expr) ? if_expr_true : if_expr_false;

expression evaluates TRUE or FALSE

TRUE: first result (before colon)

FALSE: second one (after colon)

CONTINUE

Ternary Operator Example

<?php

$a = 10;

$b = 13;

echo $a < $b ? 'Yes' : 'No';

?>

CONTROL AND LOOPING STRUCTURE

1. If/else

2. Switch

3. While

4. For loop

5. Foreach

IF/ELSE STATEMENT

Here is the example to use if/else statement

<?php// change message depending on whether// number is less than zero or not$number = -88;if ($number < 0) { echo 'That number is negative';} else { echo 'That number is either positive or zero';}

?>

THE IF-ELSEIF-ELSE STATEMENT

<?php

// handle multiple possibilities

if($answer == ‘y’) {

print "The answer was yes\n";

else if ($answer == ‘n’) {

print "The answer was no\n";

}else{

print "Error: $answer is not a valid answer\n";

}

?>

THE SWITCH-CASE STATEMENT

<?php// handle multiple possibilitiesswitch ($answer) {

case 'y':print "The answer was yes\n";break;

case 'n':print "The answer was no\n";break;

default:print "Error: $answer is not a valid answer\n";break;

}?>

WHILE LOOP

SYNTAX while (condition): code to be executed; endwhile;

EXAMPLE<?php// repeats until counter becomes 10$counter = 1;while($counter < 10){ echo $counter; $counter++;}?>

THE DO-WHILE LOOP

SYNTAX:do { code to be executed; } while (condition);

EXAMPLE<?php// repeats until counter becomes 10$counter = 1;do{ echo $counter; $counter++;}while($counter < 10);?>

THE FOR LOOP

SYNTAXfor (init; cond; incr) { code to be executed; }

init: Is mostly used to set a counter, but can be any code to be executed once at the beginning of the loop statement. cond: Is evaluated at beginning of each loop iteration. If the condition evaluates to TRUE, the loop continues and the code executes. If it evaluates to FALSE, the execution of the loop ends. incr: Is mostly used to increment a counter, but can be any code to be executed at the end of each loop.

BREAKING A LOOP

Occasionally it is necessary to exit from a loop before it has met whatever completion criteria were specified. To achieve this, the break statement must be used. The following example contains a loop that uses the break statement to exit from the loop when i = 100, even though the loop is designed to iterate 100 times:

for ($i = 0; $i < 100; $i++)

{

if ($i == 10)

{

break;

}

}

CONTINUE

Skipping Statements in Current Loop Iteration.

continue is used within looping structures to skip the rest of the current loop iteration and continue execution at the condition evaluation and then the beginning of the next iteration.

for ($i = 0; $i < 5; ++$i) {

if ($i == 2)

continue

print "$i\n";

}

EXAMPLE:

<?php

// repeat continuously until counter becomes 10

// output:

for ($x=1; $x<10; $x++) {

echo "$x ";

}

?>

ARRAY IN PHP

An array can store one or more values in a single variable name.

There are three different kind of arrays:

1. Numeric array - An array with a numeric ID key

2. Associative array - An array where each ID key is associated with a value

3. Multidimensional array - An array containing one or more arrays

FOREACH LOOP

SYNTAX:

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

<?php$fruits = array( 'a' => 'apple', 'b' => 'banana', 'p' => 'pineapple', 'g' => 'grape');?>

FOREACH LOOP

$array = ['apple', 'banana', 'orange‘];foreach ($array as $value) { $array = strtoupper($value);}foreach ($array as $key => $value) { $array[$key] = strtolower($value);}

var_dump($array);array(3) { [0]=> string(3) "APPLE" [1]=> string(3) "BANANA" [2]=> &string(3) "ORANGE"}

ERRORS AND ERROR MANAGEMENT

Errors:

Basically errors can be of one of two types

External Errors

Logic Errors (Bugs)

What about these error types?

External Errors will always occur at some point or another

External Errors which are not accounted for are Logic Errors

Logic Errors are harder to track down

PHP ERRORS

Four levels of error condition to start with

• Strict standard problems (E_STRICT)

• Notices (E_NOTICE)

• Warnings (E_WARNING)

• Errors (E_ERROR)

To enable error in PHP :

ini_set('display_errors', 1);

error_reporting(E_ALL);

PHP ERRORS EXAMPLE

// E_NOTICE :

<?php echo $x = $y + 3; ?>

Notice: Undefined variable: y

// E_WARNING

<?php $fp = fopen('test_file', 'r'); ?>

Warning: fopen(test_file): failed to open stream: No such file or directory

// E_ERROR

<?php NonFunction(); ?>

Fatal error: Call to undefined function NonFunction()

REQUIRE, INCLUDE

1. require('filename.php');

Include and evaluate the specified file

Fatal Error

2. include('filename.php');

Include and evaluate the specified file

Warning

3. require_once/include_once

If already included,won't be include again

TUTORIAL

1. Write a PHP script using a ‘do while’ loop that accept value from two input box and perform addition, subtraction, multiplication, division,modulus, square-root, square, Factorial operation on two value then display total as the output.

Example:

First value input field + select box for operator selection + second value = OUTPUT

2.Create a php function that accepts an integer value and other information like name and outputs a message based on the number entered by user in input field. Use a ‘switch’ statement for interger and display values.

For a remainder of 0, print: “Welcome ”, [name],

For a remainder of 1, print: “How are you,[name]?”

For a remainder of 2, print: “I’m doing well, Thank you”

For a remainder of 3, print: “Have a nice day”

For a remainder of 4, print: “Good-bye”

3. Write a PHP program that display series of numbers (1,2,3,4, 5....etc) in an infinite loop. The program should quit if someone hits a specific ESCAPE key.

4. Create a PHP Program that Use an associative array to assign for person name with their favourite color and print “x favourite color is y” using foreach loop in HTML table

5. Create a PHP program that get system date and convert it in different formats with usingdisplay in Indian Timezone.

1. 29-Jun-2015

2. 06 29 2013 23:05 PM

3. 29th June 2015 4:20:01

4. Tomorrow

5. Get the date of Next week from today

6. Get the date of Next monday

6.Create a Program which accept Year from selectbox and display computed age based on the Selected Value.