III B.Com(CA)-PHP -Unit 2

Unit-II: Working with Arrays: Arrays, Creating Arrays, Some Array-Related Functions. Working with Objects: Creating Objects, Object Instance. Working with Strings, Dates and Time: Formatting Strings with PHP, Investigating Strings with PHP, Manipulating Strings with PHP, Using Date and Time Functions in PHP.

Q) What Are Arrays? Explain how to create an Array. (OR) Explain different types of Arrays.

An array is a data structure that stores one or more similar type of values in a single variable . Arrays are indexed, which means that each entry is made up of a key and a value. The key is the index position, beginning with 0 and increasing incrementally by 1 with each new element in the array.  The value can be a string, an integer, or whatever we gave to it.

An array can be created using either the array ( ) function or the array operator [].

Eg:

1.  $rainbow =  array(“red”,  “orange”, “yellow”, “green”, “blue”, “indigo”, “violet”);

2.  $rainbow[ ] =  “red”;

$rainbow[ ] =  “orange”;

$rainbow[ ] =  “yellow”;

$rainbow[ ] =  “green”;

$rainbow[ ] =  “blue”;

$rainbow[ ] =  “indigo”;

$rainbow[ ] =  “violet”;

Both create a seven-element array called $rainbow, with  values starting at index position 0 and ending at index position 6.

In PHP, there are three types of arrays:

1. Indexed arrays - Arrays with numeric index
2. Associative arrays - Arrays with named keys
3. Multidimensional arrays - Arrays containing one or more arrays

1. Indexed Arrays: Indexed arrays use an index position as the  key—0,  1, 2, and so forth

Syntax: array(value1,value2,value3,etc.);

Example:

$rainbow =  array(“red”,  “orange”, “yellow”, “green”, “blue”,

“indigo”, “violet”);

2. Associative arrays: Arrays with named keys.

Synt ax:  array(key=>value, key=>value, key=>value, etc.);

Example:

$character =  array(“name”  =>  “Bob”,“occupation” =>  “superhero”, “age” =>  30,“special power” =>  “x-ray vision”);

The four keys in the $character array are name, occupation, age, and special power. The associated values are Bob, superhero, 30, and x-ray vision, respectively.

3. Multidimensional array: A multidimensional array is an array containing one or more arrays. PHP understands multidimensional arrays that are two, three, four, five, or more levels deep.

Example:

$cars = array
  (
  array("Volvo",22,18),
  array("BMW",15,13),
  array("Saab",5,2),
  array("Land Rover",17,15)
  );

Q) Write Some Array-Related Functions.

1.  count( )-This functions counts the  number of elements in an array.

Example:     $colors =  array(“blue”, “black”, “red”, “green”);
                         count($colors); return a value of 4.

2.  array_push()—This function adds one  or more elements to the  end  of an existing array.

Example:     array_push($existingArray,  “element 1”,  “element 2”,  “element 3”);

3.  array_ pop()—This function removes (and returns) the  last  element of an existing array

Example:  $last_element =  array_pop($existingArray);

4.  array_unshift( )—This function adds one  or more elements to the  beginning of an existing array.

Example: array_unshift($existingArray,  “element 1”, “element 2”, “element 3”);

5.  array_shift()—This function removes (and returns) the  first element of an existing array

Example: $first_element =  array_shift($existingArray);

6.  array_merge()—This function combines two or more existing arrays.

Example: $newArray =  array_merge($array1, $array2);

7.  array_keys()—This function returns an array containing all  the  key names within a given array.

Example: $keysArray =  array_keys($existingArray);

8.  array_values()—This function returns an array containing all  the  values within a given array.

Example: $valuesArray =  array_values($existingArray);

9.  shuffle()—This function randomizes the  elements of a given array.

Example: shuffle($existingArray);

10.         sort($arr): This function sorts the elements of an array in ascending order. String values will be arranged in ascending alphabetical order.

Example: $data = array("g", "t", "a", "s");

    sort($data);

Q) Explain Concept of Object Oriented Programming in PHP

Object Oriented is an approach to software development that models application around real world objects such as employees, cars, bank accounts, etc.

1.  Class − A class defines the properties and methods of a real world object.

2.  Object − An individual instance of the data structure defined by a class.

a.  Member Variable − these are the variables defined inside a class. This data will be invisible to the outside of the class and can be accessed via member functions.

b.  Member function − these are the function defined inside a class and are used to access object data.

3.  Inheritance – The inheritance is a way to form new classes using classes that have already been defined. The newly formed classes are called derived classes, the classes that we derive from are called base classes. Important benefits of inheritance are code reuse and reduction of complexity of a program. The derived classes (descendants) override or extend the functionality of base classes (ancestors).

4.  Polymorphism − This is an object oriented concept where same function can be used for different purposes. For example function name will remain same but it make take different number of arguments and can do different task.

5.  Overloading − a type of polymorphism in which some or all of operators have different implementations depending on the types of their arguments.

6.  Data Abstraction − Any representation of data in which the implementation details are hidden (abstracted).

7.  Encapsulation − refers to a concept where we encapsulate all the data and member functions together to form an object.

8.  Constructor − refers to a special type of function which will be called automatically whenever there is an object formation from a class.

9.  Destructor − refers to a special type of function which will be called automatically whenever an object is deleted or goes out of scope

Q) Explain how to create an Objects and Class in PHP and how to access properties and methods in PHP

Objects are basic building blocks of a PHP OOP program. An object is a combination of data and methods. In a OOP program, we create objects. These objects communicate together through methods. Each object can receive messages, send messages, and process data.
There are two steps in creating an object. First, we create a class. A class is a template for an object. It is a blueprint which describes the state and behavior that the objects of the class all share. A class can be used to create many objects. Objects created at runtime from a class are called instances of that particular class.

1.  A class can be declared using the class keyword, followed by the name of the class and a pair of curly braces ({}), A class definition includes the class name and the properties and methods of the class. Class names are case-insensitive and must conform to the rules for PHP identifiers.

Syntax for a class definition:

class classname [ extends baseclass ]

{

    [ var $property [ = value ]; ... ]

    [ function functionname (args) {

          // code 

      }

      ...

    ]

}

2.  Once a class has been defined, objects can be created from the class with the new keyword.

$object = new Class;

Example:  $rasmus = new Person;

Some classes permit to pass arguments to the new call.

Example: $object = new Person('Fred', 35);

3.  Accessing Properties and Methods

The variables declared inside an object are called properties.Once an object is created,we can use the -> notation to access methods and properties of the object:

$object->propertyname

$object->methodname([arg, ... ])

For example:

printf("Rasmus is %d years old.\n", $rasmus->age);  // property access

$rasmus->birthday();                                // method call

$rasmus->set_age(21);                               // method call with arguments

Methods are functions, so they can take arguments and return a value:

$clan = $rasmus->family('extended')

Example:

<?php

class Rectangle

{

        public $length = 0;

    public $width = 0;

   

    public function getPerimeter(){

        return (2 * ($this->length + $this->width));

    }

   

    public function getArea(){

        return ($this->length * $this->width);

    }

}

?>

Save the above file as Rectangle.php

<?php

require "Rectangle.php";

$obj = new Rectangle;

echo $obj->length . "<br>";

echo $obj->width . "<br>";

$obj->length = 30;

$obj->width = 20;

echo $obj->length . "<br>";

echo $obj->width . "<br>";

echo $obj->getPerimeter() . "<br>";

echo $obj->getArea() . "<br>";

?>                                        

Q) Write a note on Constructors and Destructors.

Constructor: A constructor is a special kind of a method. It is automatically called when the object is created. The purpose of the constructor is to initiate the state of the object. The name of the constructor in PHP is __construct() (with two underscores).

Destructor: The magic method __destruct() (known as destructor) is executed automatically when the object is destroyed. A destructor function cleans up any resources allocated to an object once the object is destroyed.

Example:

<?php

class MyClass

{

    public function __construct(){

        echo 'The class "' . __CLASS__ . '" was initiated!<br>';

    }

   

    public function __destruct(){

        echo 'The class "' . __CLASS__ . '" was destroyed.<br>';

    }

}

$obj = new MyClass;

 echo "The end of the file is reached.<br>";

?>

                                    

Q) Explain Object Inheritance.

Inheritance: The inheritance is a way to form new classes using classes that have already been defined. The newly formed classes are called derived classes, the classes that we derive from are called base classes. Important benefits of inheritance are code reuse and reduction of complexity of a program. The derived classes (descendants) override or extend the functionality of base classes (ancestors).

Example:

<?php

class Base {

    function __construct() {

       echo "Construction of Base class \n";

    }

}

class Derived extends Base {

    function __construct() {

        parent::__construct();

        echo "Construction of Derived class \n";

    }

}

$obj1 = new Base();

$obj2 = new Derived();

?>

Q) Explain how to format Strings with PHP.

String: A string is a sequence of letters, numbers, special characters and arithmetic values or combination of all. The simplest way to create a string is to enclose the string literal (i.e. string characters) in single quotation marks (').

Double quotation marks (")also use to declare strings. However, single and double quotation marks work in different ways. Strings enclosed in single-quotes are treated almost literally, whereas the strings delimited by the double quotes replaces variables with the string representations of their values as well as specially interpreting certain escape sequences.

Formatting Strings:

1.  escape-sequence characters:

·         \n is replaced by the newline character

·         \r is replaced by the carriage-return character

·         \t is replaced by the tab character

·         \$ is replaced by the dollar sign itself ($)

·         \" is replaced by a single double-quote (")

·         \\ is replaced by a single backslash (\)

Example:

<?php

$my_str = 'World';

echo "Hello, $my_str!<br>";      // Displays: Hello World!

echo 'Hello, $my_str!<br>';      // Displays: Hello, $my_str!

echo '<pre>Hello\tWorld!</pre>'; // Displays: Hello\tWorld!

echo "<pre>Hello\tWorld!</pre>"; // Displays: Hello   World!

echo 'I\'ll be back';            // Displays: I'll be back

?>

2.  printf():  The printf() function requires a string argument, known as a format control string. It also accepts additional arguments of different types. The different types of formatting strings of PHP are as shown below.

printf(:formatting control strings”,var1,var2…);

FORMAT SPECIFIERS:

%b	binary
%c	ASCII character
%d	signed decimal number
%e	scientific number
%u	unsigned decimal number
%f	float with local settings
%F	float without local settings
%o	octal number
%x	lowercase hexadecimal
%X	uppercase hexadecimal

Example:

<?php

$number =  543;

printf(“Decimal: %d<br/>”, $number);

printf(“Binary: %b<br/>”, $number);

printf(“Double:  %f<br/>”, $number);

printf(“Octal: %o<br/>”, $number);

printf(“String: %s<br/>”, $number);

printf(“Hex (lower): %x<br/>”, $number);

printf(“Hex (upper): %X<br/>”, $number);

?>

3.  padding specifier:

The string can be padded by leading characters. The padding specifier should directly follow the percent sign that begins a conversion specification

<?php

printf("%04d", 36);

// prints "0036"

?>

4.  Field Width: A field width specifier is an integer that should be placed after the percent sign  that begins a conversion specification.

Example:

<?php

printf(“%20s\n”,  “Books”);

printf(“%20s\n”,  “CDs”);

printf(“%20s\n”,  “DVDs”);

printf(“%20s\n”,  “Games”);

printf(“%20s\n”,  “Magazines”);

?>

Q) How to Investigating Strings in PHP?

1.  Indexing Strings: A string as an array of characters, and thus strings can be access with the individual characters.

Example:

<?php

$test =  “phpcoder”;

echo $test[0]; // prints  “p”

echo $test[4]; // prints  “o”

?>

2.  strlen():The strlen() function is used to calculate the number of characters inside a string. This function requires a string as its argument and returns an integer representing the number of characters in the string.

Example:

<?php

$membership =  “pAB7”;

if (strlen($membership) ==  4)  {

echo  “<p>Thank you!</p>”;

}  else  {

echo  “<p>Your membership number must  be  four characters  long.</p>”;

}

?>

3.  strstr():the  strstr() function is used to test  whether a string exists  within another string or not. This function requires two arguments: the  source string and the  substring to find  within it. The function returns false if it cannot find  the  substring; otherwise, it returns the  portion of the  source string, beginning with  the  substring.

Example:

<?php

$membership =  “pAB7”;

if (strstr($membership, “AB”)) {

echo  “<p>Your membership expires  soon!</p>”;

}  else  {

echo  “<p>Thank you!</p>”;

}

?>

4.  strpos(): The strpos() function is used to  tells whether a string exists  within a larger string as well as where it is found. The strpos() function requires two arguments: the  source string and the  substring to  seeking. The function also accepts an optional third argument, an integer representing the index from which you want to start searching.  If the  substring does  not  exist,  strpos() returns false; otherwise, it returns the index at which the  substring begins.

Example:

<?php

$membership =  “mz00xyz”;

if (strpos($membership,  “mz”) ===  0)  {

echo “Hello  mz!”;

}

?>

5.  substr(): The substr() function returns a string based on  the  start index and length of the characters. This function requires two arguments: a source string and the starting index. Using  these arguments, the  function returns all  the  characters  from  the  starting index to the  end  of the  string. It also (optionally) provide a third argument—an integer representing the length of the string to returned. If this third argument is present, substr( ) returns only that number of characters, from  the  start index onward:

Example:

<?php

$test =  “phpcoder”;

echo substr($test,3).”<br/>”;   // prints  “coder”

echo substr($test,3,2).”<br/>”; // prints  “co”

?>

Q) How to Manipulating Strings with PHP

PHP provides many built-in functions for manipulating strings like calculating the length of a string, find substrings or characters, replacing part of a string with different characters, take a string apart, and many others.

1.  The trim() function shaves any whitespace characters, including newlines, tabs, and spaces, from  both the  start and end  of a string.

2.  The str_word_count() function counts the number of words in a string

3.  The str_replace() replaces all occurrences of the search text within the target string.

4.  The strrev() function reverses a string.

5.  The strpos() function is used to search for a string or character within a string.

6.  The strtoupper() function converts string into upper case.

7.  The Strtolower( ) function converts string to lowercase characters.

8.  The ucwords() function makes the  first letter of every  word  in a string into uppercase

9.  the  ucfirst() function capitalizes only  the  first letter in a string.

Some examples:

example:

<?php

$text =  “\t\tlots  of room   to breathe       “;

echo “<pre>$text</pre>”;

// prints  “            lots  of room   to breathe       “;

$text =  trim($text);

echo “<pre>$text</pre>”;

// prints “lots of room   to breathe”;

?>

Example:

<?php

$membership =  “mz11xyz”;

$membership =  substr_replace($membership, “12”, 2, 2);

echo “New  membership number: $membership”;

// prints “New  membership number:  mz12xyz”

?>

Q)  Explain Using Date and Time Functions in PHP.

1.  time():  time() function gives information about the  current date and time.

syntax:

echo time();

TimeStamp: A Unix Timestamp is the number of seconds that have passed since January 1, January, 1970 00:00:00 Greenwich Mean Time (GMT). Currently, the timestamp is 1513422833, but since it changes every second, the number will increase if you refresh the page

Example:

<?php

echo time();

// sample output:  1326853185

// this  represents January 17, 2012 at  09:19PM

?>

2.The PHP Date() Function: The date() function accepts two arguments. The first argument is the format that you want the timestamp in. The second argument (optional) is the timestamp that you want formatted. If no timestamp is supplied, the current timestamp will be used.

Syntax:

<?php

date(format,[timestamp]);

?>

PHP provides over thirty-five case-sensitive characters that are used to format the date and time. These characters are:

	Character	Description	Example
Day	J	Day of the Month, No Leading Zeros	1 - 31
Day	D	Day of the Month, 2 Digits, Leading Zeros	01 - 31
Day	D	Day of the Week, First 3 Letters	Mon - Sun
Day	l (lowercase 'L')	Day of the Week	Sunday - Saturday
Day	N	Numeric Day of the Week	1 (Monday) - 7 (Sunday)
Day	W	Numeric Day of the Week	0 (Sunday) - 6 (Saturday)
Day	S	English Suffix For Day of the Month	st, nd, rd or th
Day	Z	Day of the Year	0 - 365
Week	W	Numeric Week of the Year (Weeks Start on Mon.)	1 - 52
Month	M	Textual Representation of a Month, Three Letters	Jan - Dec
Month	F	Full Textual Representation of a Month	January - December
Month	M	Numeric Month, With Leading Zeros	01 - 12
Month	N	Numeric Month, Without Leading Zeros	1 - 12
Month	T	Number of Days in the Given Month	28 - 31
Year	L	Whether It's a Leap Year	Leap Year: 1, Otherwise: 0
Year	Y	Numeric Representation of a Year, 4 Digits	1999, 2003, etc.
Year	Y	2 Digit Representation of a Year	99, 03, etc.
Time	A	Lowercase Ante Meridiem & Post Meridiem	am or pm
Time	A	Uppercase Ante Meridiem & Post Meridiem	AM or PM
Time	B	Swatch Internet Time	000 - 999
Time	G	12-Hour Format Without Leading Zeros	1 - 12
Time	G	24-Hour Format Without Leading Zeros	0 - 23
Time	H	12-Hour Format With Leading Zeros	01 - 12
Time	H	24-Hour Format With Leading Zeros	00 - 23
Time	I	Minutes With Leading Zeros	00 - 59
Time	S	Seconds With Leading Zeros	00 - 59
Timezone	E	Timezone Identifier	Example: UTC, Atlantic
Timezone	I (capital i)	Whether Date Is In Daylight Saving Time	1 if DST, otherwise 0
Timezone	O	Difference to Greenwich Time In Hours	Example: +0200
Timezone	P	Difference to Greenwich Time, With Colon	Example: +02:00
Timezone	T	Timezone Abbreviation	Examples: EST, MDT ...
Timezone	Z	Timezone Offset In Seconds	-43200 through 50400

Using a combination of these characters and commas, periods, dashes, semicolons and backslashes, you can now format dates and times.

<?php
  // Will Echo: 3:13 AM Saturday, December 16, 2017
  echo date("g:i A l, F d, Y");
  // Will Echo: 2017-12-15
  $yesterday = strtotime("yesterday");
  echo date("Y-m-d", $yesterday);
?>

3. The PHP Strtotime() Function: The strtotime() function accepts an English datetime description and turns it into a timestamp.

Some examples are:

<?php
  echo strtotime("now") . "<br />";
  echo strtotime("tomorrow") . "<br />";
  echo strtotime("yesterday") . "<br />";
  echo strtotime("10 September 2000") . "<br />";
  echo strtotime("+1 day") . "<br />";
  echo strtotime("+1 week") . "<br />";
  echo strtotime("+1 week 2 days 4 hours 2 seconds") . "<br />";
  echo strtotime("next Thursday") . "<br />";
  echo strtotime("last Monday") . "<br />";
  echo strtotime("4pm + 2 Hours") . "<br />";
  echo strtotime("now + 2 fortnights") . "<br />";
  echo strtotime("last Monday") . "<br />";
  echo strtotime("2pm yesterday") . "<br />";
  echo strtotime("7am 12 days ago") . "<br />";
?>