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PHP
Unit2

1. What is an array?

An array is a data structure that can store a collection of values under a single variable name in PHP. It allows you to store and access multiple values in a single variable. In PHP, arrays can be indexed by a numerical index or a string index.

Here is an example of creating an array in PHP:

vros.php
<?php
 
// Creating an array with numerical index
$numbers = array(1, 2, 3, 4, 5);
 
// Creating an array with string index
$person = array("name" => "Vros", "age" => 30, "city" => "New York");
 
?>

In the above example, we create two arrays, one with a numerical index and the other with a string index. The first array $numbers contains a list of numerical values, while the second array $person contains three key-value pairs where each key is a string and its corresponding value is assigned.

Arrays in PHP can be accessed using their index values. Here is an example:

vros.php
<?php
 
// Accessing array elements
echo $numbers[2];    // Output: 3
echo $person["name"];   // Output: Vros
 
?>

In the above example, we access the third element of the $numbers array using its numerical index value of 2, and we access the value of the "name" key in the $person array using its string index value.

Arrays are a powerful data structure in PHP that can be used in a variety of ways to store and manipulate data.

2. How to create an array? Explain with example.

In PHP, there are several ways to create an array. Here are three common methods:

Method 1: Using the array() function

You can use the array() function to create an array in PHP. This method is useful when you need to create an array with specific values.

Here is an example:

vros.php
// Creating an array with specific values
$fruits = array("Apple", "Banana", "Orange");

In this example, we create an array named $fruits that contains three elements, "Apple", "Banana", and "Orange".

Method 2: Using square brackets

You can also create an array using square brackets []. This method is useful when you need to create an empty array and add values later.

Here is an example:

vros.php
// Creating an empty array and adding values later
$numbers = [];
$numbers[] = 1;
$numbers[] = 2;
$numbers[] = 3;

In this example, we create an empty array named $numbers and then add three values to it using the [] syntax.

Method 3: Using the range() function

If you need to create an array with a range of values, you can use the range() function. This method is useful when you need to create an array with a large number of consecutive values.

Here is an example:

vros.php
// Creating an array with a range of values
$numbers = range(1, 10);

In this example, we create an array named $numbers that contains the values 1 to 10.

Once you have created an array, you can access its elements using their index values. For example:

vros.php
// Accessing array elements
echo $fruits[0];    // Output: Apple
echo $numbers[3];   // Output: 4

In this example, we access the first element of the $fruits array using its index value of 0, and we access the fourth element of the $numbers array using its index value of 3.

3. What is string?

In PHP, a string is a sequence of characters that represents text. It can include letters, numbers, symbols, and spaces. Strings are used extensively in PHP for things like input and output, storing and manipulating data, and constructing HTML and XML documents.

A string can be defined in PHP using single quotes ' ' or double quotes " ". Here are some examples:

vros.php
 
$name = 'Vros';
$message = "Hello, $name!";
 
echo $name;      // Output: Vros
echo $message;   // Output: Hello, Vros!

In this example, we create two strings: $name and $message. $name is defined using single quotes and contains the value "Vros". $message is defined using double quotes and includes a variable $name, which is evaluated and replaced with its value when the string is output.

Strings in PHP can be manipulated using a variety of functions such as strlen(), strpos(), substr(), str_replace(), and more. These functions allow you to perform operations like getting the length of a string, finding the position of a substring within a string, extracting a portion of a string, and replacing characters in a string.

vros.php
$text = "The quick brown fox jumps over the lazy dog.";
 
// Getting the length of a string
echo strlen($text);     // Output: 44
 
// Finding the position of a substring
echo strpos($text, "brown");    // Output: 10
 
// Extracting a portion of a string
echo substr($text, 16, 5);      // Output: fox j
 
// Replacing characters in a string
echo str_replace("lazy", "sleepy", $text);   // Output: The quick brown fox jumps over the sleepy dog.

In this example, we create a string $text that contains the famous pangram "The quick brown fox jumps over the lazy dog." We then use various string functions to perform operations like getting the length of the string, finding the position of a substring within the string, extracting a portion of the string, and replacing characters in the string.

4. What is function?

In PHP, a function is a block of code that can be called by name and performs a specific task. Functions are used to make code modular, easier to read and maintain, and to avoid code repetition.

A function in PHP is defined using the function keyword, followed by the function name and a set of parentheses. Any parameters that the function accepts are specified within the parentheses. The function code is enclosed in curly braces { }. Here's an example of a simple function:

vros.php
function sayHello() {
  echo "Hello, world!";
}

In this example, we define a function named sayHello() that simply outputs the message "Hello, world!". To call this function, we simply write its name followed by a set of parentheses:

vros.php
sayHello();   // Output: Hello, world!

Functions can also accept parameters, which are values passed to the function when it is called. These parameters can be used inside the function to perform operations or return a value. Here's an example:

vros.php
function addNumbers($a, $b) {
  return $a + $b;
}
 
$result = addNumbers(3, 5);
echo $result;   // Output: 8

In this example, we define a function named addNumbers() that accepts two parameters $a and $b. The function adds these two numbers together and returns the result using the return keyword. We then call the function with the values 3 and 5 and store the result in a variable $result, which we output to the screen.

5. How to extract data from array? Explain with example.

In PHP, you can extract data from an array using array indexing. Array indexing refers to accessing a specific element of an array by its position or key.

To extract data from an array by position, you can use square brackets [] with the index number of the element you want to access. Array indexing starts at 0 for the first element, so the index number of the second element is 1, the index number of the third element is 2, and so on. Here's an example:

$fruits = array("apple", "banana", "cherry", "date");
echo $fruits[2];   // Output: cherry

In this example, we define an array $fruits that contains four elements. We then use array indexing to access the third element of the array (which has an index of 2) and output its value "cherry" to the screen.

To extract data from an associative array by key, you can use square brackets [] with the key name of the element you want to access. Here's an example:

$person = array("name" => "John", "age" => 30, "city" => "New York");
echo $person["age"];   // Output: 30

In this example, we define an associative array $person that contains three elements, each with a key and a value. We then use array indexing to access the value of the "age" key and output it to the screen.

You can also use a loop like foreach() to extract data from all elements of an array. The foreach() loop iterates over each element of an array and assigns the value of the current element to a variable. Here's an example:

$numbers = array(1, 2, 3, 4, 5);
 
foreach ($numbers as $number) {
  echo $number . " ";
}
 
// Output: 1 2 3 4 5

In this example, we define an array $numbers that contains five elements. We then use a foreach() loop to iterate over each element of the array and output its value to the screen. The foreach() loop assigns the value of the current element to a variable $number, which we use to output the value of each element.

6. Enlist types of arrays. Describe with example.

In PHP, there are three types of arrays: indexed arrays, associative arrays, and multidimensional arrays.

  • Indexed Arrays: An indexed array is a type of array in which each element is identified by an index number that starts from 0 and increments by 1 for each element. An indexed array can be created using the array() function or the shorthand [] notation. Here's an example:
vros.php
$fruits = array("apple", "banana", "cherry");
echo $fruits[1];   // Output: banana

In this example, we define an indexed array $fruits that contains three elements. We then use array indexing to access the second element of the array (which has an index of 1) and output its value "banana" to the screen.

  • Associative Arrays: An associative array is a type of array in which each element is identified by a unique key instead of an index number. An associative array can be created using the array() function and the => notation to specify the key-value pairs. Here's an example:
vros.php
phpCopy code
$person = array("name" => "John", "age" => 30, "city" => "New York");
echo $person["age"];   // Output: 30

In this example, we define an associative array $person that contains three elements, each with a key and a value. We then use array indexing to access the value of the "age" key and output it to the screen.

  • Multidimensional Arrays: A multidimensional array is a type of array in which each element can itself be an array, forming a matrix-like structure. A multidimensional array can be created by nesting arrays inside arrays. Here's an example:
vros.php
$matrix = array(
  array(1, 2, 3),
  array(4, 5, 6),
  array(7, 8, 9)
);
 
echo $matrix[1][2];   // Output: 6

In this example, we define a multidimensional array $matrix that contains three arrays, each representing a row of the matrix. We then use array indexing to access the value of the element in the second row and third column of the matrix (which has an index of [1][2]) and output its value "6" to the screen.

7. Write the difference between index and associative array with example.

The main difference between indexed and associative arrays in PHP is the way elements are accessed within the array.

  • Indexed Array: An indexed array is an array in which elements are accessed by their numerical index, which starts from 0 and increases by 1 for each element in the array. The elements in an indexed array are stored in a specific order based on their index. Here's an example of an indexed array:
vros.php
$fruits = array("apple", "banana", "cherry");
echo $fruits[1];   // Output: banana

In this example, the $fruits array is an indexed array with three elements. The element "apple" has an index of 0, "banana" has an index of 1, and "cherry" has an index of 2. We can access the element "banana" by referring to its index number, which is 1.

  • Associative Array: An associative array is an array in which elements are accessed by their associated keys, which can be strings or integers. The elements in an associative array are not stored in any particular order, and each element is associated with a unique key. Here's an example of an associative array:
vros.php
$person = array("name" => "John", "age" => 30, "city" => "New York");
echo $person["age"];   // Output: 30

In this example, the $person array is an associative array with three elements. The element with the key "name" has the value "John", the element with the key "age" has the value 30, and the element with the key "city" has the value "New York". We can access the element with the key "age" by using its key name, which is "age".

To summarize, indexed arrays use numerical indexes to access elements, whereas associative arrays use keys to access elements. Indexed arrays store elements in a specific order, whereas associative arrays do not.

8. How to add image in PHP? Explain with example.

To add an image in PHP, you can use the <img> tag with the src attribute set to the path of the image file. Here's an example:

<!DOCTYPE html>
<html>
<head>
	<title>PHP Image Example</title>
</head>
<body>
	<h1>PHP Image Example</h1>
	<img src="image.jpg" alt="Example Image">
</body>
</html>

In this example, we have an HTML document with a heading and an image. The img tag has a src attribute set to "image.jpg", which is the path to the image file. The alt attribute provides alternative text that can be displayed if the image cannot be loaded for some reason.

9. Define the terms:

  • Array: An array is a data structure in PHP that allows you to store multiple values in a single variable. The values in an array can be of any data type, such as integers, strings, or even other arrays. Each value in an array is identified by a unique key, which can be either a numerical index or a string.
  • String: A string is a sequence of characters in PHP, such as letters, numbers, symbols, and spaces. In PHP, strings are used to represent textual data, and they can be enclosed in either single quotes ('') or double quotes (""). You can perform various operations on strings, such as concatenation, substring extraction, and string manipulation.
  • Function: A function is a block of code in PHP that performs a specific task or set of tasks. Functions are used to organize code into reusable modules, which can be called from other parts of the code. In PHP, functions are defined using the function keyword, followed by the function name and a set of parentheses that may contain arguments. When a function is called, the arguments are passed into the function, and the function returns a value (if applicable).

10. How to create a function? Explain with example.

To create a function in PHP, you need to follow these steps:

  1. Use the function keyword, followed by the function name, to define the function.
  2. Use parentheses to enclose the function arguments (if any).
  3. Use curly braces to enclose the function code.
  4. If the function returns a value, use the return keyword, followed by the value.

Here's an example of a simple function that takes two numbers as arguments and returns their sum:

vros.php
function add_numbers($num1, $num2) {
  $sum = $num1 + $num2;
  return $sum;
}

In this example, we have defined a function called add_numbers that takes two arguments ($num1 and $num2). Inside the function, we calculate the sum of the two numbers and store it in a variable called $sum. We then use the return keyword to return the value of $sum to the calling code.

To call this function, we can simply use its name, followed by the arguments (in parentheses), like this:

vros.php
$total = add_numbers(10, 20);
echo "The sum is: " . $total;

In this example, we have called the add_numbers function with the arguments 10 and 20. The function returns the sum of the two numbers (30), which is then stored in the variable $total. We can then use the echo statement to display the value of $total on the screen.

11. State advantages of functions in PHP?

  1. Reusability: Functions allow you to write a block of code once and reuse it in multiple parts of your program. This can save time and effort, and make your code more modular and maintainable.
  2. Modularity: Functions allow you to break down a large program into smaller, more manageable modules. This can make your code easier to read, debug, and maintain.
  3. Encapsulation: Functions can encapsulate code and data, allowing you to hide the details of the implementation from the calling code. This can make your code more secure and easier to change in the future.
  4. Abstraction: Functions can provide an abstraction layer between the calling code and the implementation, allowing you to change the underlying implementation without affecting the calling code.
  5. Testing: Functions can make it easier to test your code, as you can isolate a specific block of code and test it independently of the rest of the program.

12. Compare string and array.

Strings are a sequence of characters, while arrays are an ordered collection of values. Strings store a single value, while arrays can store multiple values of any data type. Strings have elements that are individual characters, while arrays have elements that can be accessed using indexes. The size of a string is determined by the number of characters it contains, while the size of an array is determined by the number of elements it contains.

Similarities:

  • Both strings and arrays can hold multiple values (characters in the case of strings, and any type of data in the case of arrays).
  • Both strings and arrays can be accessed using indexes (numeric indexes for arrays, and string indexes for strings).

Differences:

  • Strings are a sequence of characters, while arrays are a collection of values of any type.
  • Strings have a fixed length (once created), while arrays can grow or shrink in size dynamically.
  • Strings can be treated as a single value, while arrays require multiple values to be accessed and manipulated.
  • Strings have special functions and operations that are specific to strings, while arrays have their own set of functions and operations that are specific to arrays.

13. With the help of example describe traversing of array.

Traversing an array in PHP means accessing each element of the array one by one. There are different ways to traverse an array in PHP, such as using a for loop, a foreach loop, or a while loop. Here is an example of traversing an array using a for loop:

vros.php
$numbers = array(2, 4, 6, 8, 10);
 
for($i=0; $i<count($numbers); $i++) {
  echo $numbers[$i] . " ";
}

In this example, we first define an array called $numbers that contains five elements. We then use a for loop to traverse the array. The loop runs for each index of the array, from 0 to the length of the array minus 1. For each index, we print the value of the corresponding element of the array using the index. The output of this code will be:

vros.php
2 4 6 8 10

This is just one example of traversing an array in PHP. Depending on the situation, other methods such as using a foreach loop or a while loop might be more appropriate.

14. How to convert arrays into variables and vice-versa.

In PHP, you can convert an array into variables using the extract() function. This function takes an array as input and creates variables with the same names as the keys of the array, and assigns the corresponding values to those variables. Here is an example:

vros.php
$data = array('name' => 'John', 'age' => 30, 'city' => 'New York');
 
extract($data);
 
echo $name; // Output: John
echo $age; // Output: 30
echo $city; // Output: New York

In this example, we first define an array called $data that contains three key-value pairs. We then use the extract() function to convert the array into variables. The function creates three variables called $name, $age, and $city, and assigns the corresponding values to those variables. We can then access the values of those variables directly.

To convert variables into an array, you can use the compact() function. This function takes variable names as input and creates an array with keys that are the same as the variable names, and values that are the values of those variables. Here is an example:

vros.php
$name = 'John';
$age = 30;
$city = 'New York';
 
$data = compact('name', 'age', 'city');
 
print_r($data);

In this example, we define three variables called $name, $age, and $city. We then use the compact() function to convert these variables into an array called $data. The function creates an array with three key-value pairs, where the keys are the same as the variable names and the values are the values of those variables. We then use the print_r() function to print the contents of the $data array. The output of this code will be:

vros.php
Array
(
    [name] => John
    [age] => 30
    [city] => New York
)

This is how you can convert arrays into variables and vice-versa in PHP.

15. Which operations performed on string in PHP?

In PHP, you can perform various operations on strings. Here are some of the most common operations:

  • String concatenation: You can concatenate two or more strings using the dot (.) operator. For example:
vros.php
$str1 = 'Hello';
$str2 = 'world';
$result = $str1 . ' ' . $str2;
echo $result; // Output: Hello world
  • String length: You can get the length of a string using the strlen() function. For example:
vros.php
$str = 'Hello world';
$length = strlen($str);
echo $length; // Output: 11
  • Substring: You can extract a substring from a string using the substr() function. For example:
vros.php
$str = 'Hello world';
$substring = substr($str, 6, 5);
echo $substring; // Output: world
  • String case: You can convert a string to uppercase or lowercase using the strtoupper() and strtolower() functions, respectively. For example:
vros.php
$str = 'Hello world';
$uppercase = strtoupper($str);
$lowercase = strtolower($str);
echo $uppercase; // Output: HELLO WORLD
echo $lowercase; // Output: hello world
  • String replace: You can replace a part of a string with another string using the str_replace() function. For example:
vros.php
$str = 'Hello world';
$newstr = str_replace('world', 'PHP', $str);
echo $newstr; // Output: Hello PHP

These are just some of the operations that can be performed on strings in PHP. There are many other functions and methods available for working with strings in PHP.

16. Enlist four string related function with example.

  • strlen() - Returns the length of a string
vros.php
Syntax: strlen(string)
 
Example:
$str = "Hello, world!";
$len = strlen($str);
echo $len; // Output: 13
  • substr() - Returns a part of a string
vros.php
Syntax: substr(string, start, length)
 
Example:
$str = "Hello, world!";
$sub = substr($str, 7, 5);
echo $sub; // Output: world
  • str_replace() - Replaces a string with another string
vros.php
Syntax: str_replace(find, replace, string)
 
Example:
$str = "Hello, world!";
$newstr = str_replace("world", "PHP", $str);
echo $newstr; // Output: Hello, PHP!
  • strpos() - Searches for a string inside another string and returns the position of its first occurrence
vros.php
Syntax: strpos(string, search, offset)
 
Example:
$str = "Hello, world!";
$pos = strpos($str, "world");
echo $pos; // Output: 7

17. Explain the following types of functions with example.

  • User defined functions: User-defined functions are those functions which are created by the user as per their requirements. They help in reducing the code redundancy and improving the code's reusability. User-defined functions in PHP are defined using the function keyword, followed by the function name, and the function's parameters enclosed in parentheses. The function body is enclosed in curly braces {}. Here is an example of a user-defined function that takes two parameters and returns their sum:
vros.php
function add($a, $b) {
  $sum = $a + $b;
  return $sum;
}
 
$result = add(2, 3);
echo $result; // Output: 5
  • Variable functions: Variable functions are those functions whose name is dynamically set using a string variable. To use a variable function, the variable should contain the name of a valid function. Here is an example of a variable function that takes a function name as a string and calls it:
vros.php
function say_hello() {
  echo "Hello, world!";
}
 
$func_name = "say_hello";
$func_name(); // Output: Hello, world!
  • Anonymous functions: Anonymous functions, also known as closures, are functions without a specified name. They can be assigned to variables or passed as arguments to other functions. Anonymous functions are defined using the function keyword, followed by the function's parameters and the function body. Here is an example of an anonymous function that takes two parameters and returns their sum:
vros.php
$add = function($a, $b) {
  $sum = $a + $b;
  return $sum;
};
 
$result = $add(2, 3);
echo $result; // Output: 5

18. How to create PDF in PHP? Describe with example.

Creating PDF files in PHP can be done using various third-party libraries such as TCPDF, FPDF, or mPDF. Here's an example of using TCPDF to create a simple PDF document in PHP:

  1. First, download the TCPDF library from its official website and extract it to your project directory.
  2. Create a new PHP file and include the TCPDF library file.
vros.php
require_once('tcpdf/tcpdf.php');
  1. Create a new TCPDF object and set the document properties such as page orientation, unit of measurement, and page format.
vros.php
$pdf = new TCPDF(PDF_PAGE_ORIENTATION, PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);
$pdf->SetCreator(PDF_CREATOR);
$pdf->SetAuthor('John Doe');
$pdf->SetTitle('My PDF');
$pdf->SetSubject('Generating PDFs in PHP');
$pdf->SetKeywords('PDF, PHP, TCPDF');
  1. Add a new page to the PDF document and set the font.
vros.php
$pdf->AddPage();
$pdf->SetFont('helvetica', '', 12);
  1. Add some content to the PDF document.
vros.php
$pdf->Write(0, 'Hello, world!');
  1. Output the PDF document.
vros.php
$pdf->Output('example.pdf', 'I');

The Output() method takes two parameters: the first parameter is the filename of the PDF document, and the second parameter is the destination of the PDF document. In the above example, I is used to output the PDF document directly to the browser.

Overall, this example creates a new TCPDF object, sets the document properties, adds a new page, sets the font, adds some content, and outputs the PDF document. You can customize the PDF document as per your requirements using various TCPDF methods.

19. How to scaling an image in PHP?

To scale an image in PHP, you can use the imagecopyresampled() function. This function copies a rectangular portion of one image onto another image, and resamples the image to a new size.

Here is an example code that scales an image to a new size:

vros.php
// Load the original image
$filename = "original_image.jpg";
$original_image = imagecreatefromjpeg($filename);
 
// Get the original image dimensions
$original_width = imagesx($original_image);
$original_height = imagesy($original_image);
 
// Define the new image dimensions
$new_width = 500;
$new_height = 300;
 
// Create a new blank image with the new dimensions
$new_image = imagecreatetruecolor($new_width, $new_height);
 
// Copy and resample the original image onto the new image
imagecopyresampled($new_image, $original_image, 0, 0, 0, 0, $new_width, $new_height, $original_width, $original_height);
 
// Output the new image to the browser or save it to a file
header('Content-Type: image/jpeg');
imagejpeg($new_image);
imagedestroy($new_image);
imagedestroy($original_image);

In this example, we first load the original image using the imagecreatefromjpeg() function. Then, we get the original image dimensions using the imagesx() and imagesy() functions.

Next, we define the new dimensions for the scaled image. We then create a new blank image using the imagecreatetruecolor() function.

Finally, we copy and resample the original image onto the new image using the imagecopyresampled() function, and output the new image to the browser or save it to a file using the imagejpeg() function.

20. Explain array _flip() function with example.

The array_flip() function in PHP is used to flip or exchange the keys with their corresponding values in an array. The function returns an array with keys from the input array as values, and values from the input array as keys.

Syntax:

vros.php
array_flip(array $array): array

Example:

vros.php
// Define an array
$fruits = array("apple", "banana", "cherry", "date");
 
// Flip the keys and values
$flipped_array = array_flip($fruits);
 
// Output the result
print_r($flipped_array);

Output:

vros.php
Array
(
    [apple] => 0
    [banana] => 1
    [cherry] => 2
    [date] => 3
)

In the above example, the array_flip() function takes an array of fruits as input and returns an array with keys and values flipped, where the keys become the values, and the values become the keys. The resulting array contains the original values as keys and their corresponding keys as values.

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