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
By
www.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. Boolean
2. integer
3. float (floating-point number, aka double)
4. string
Two compound types:
5. array
6. object
And finally three special types:
7. resource
8. NULL
9. callable

CONTINUE...
Integer : used to specify numeric value
SYNTAX:
<?php $variable = 10; ?>
Float : used to specify real numbers
SYNTAX:
<?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 = "Hellon 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 constant
value: Specifies the value of the constant
case-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 3
2.5
% Modulus(division
remainder)
5%2,10%8 1
2
++ 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($answer == ‘y’) {
print "The answer was yesn";
else if ($answer == ‘n’) {
print "The answer was non";
}else{
print "Error: $answer is not a valid answern";
}
?>

THE SWITCH-CASE STATEMENT
<?php
// handle multiple possibilities
switch ($answer) {
case 'y':
print "The answer was yesn";
break;
case 'n':
print "The answer was non";
break;
default:
print "Error: $answer is not a valid answern";
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 {
} while (condition);
EXAMPLE
<?php
// repeats until counter becomes 10
$counter = 1;
do{
echo $counter;
$counter++;
}while($counter < 10);
?>

THE FOR LOOP
SYNTAX
for (init; cond; incr)
{
}
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 ($i == 2)
continue
print "$in";
}

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)
{
}
<?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.

PHP - DataType,Variable,Constant,Operators,Array,Include and require

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PHP - DataType,Variable,Constant,Operators,Array,Include and require