Discuss about various functions used in PHP with suitable coding examples.

Marks: 8

• PHP offers a vast collection of built-in functions that simplify common programming tasks. These functions can be broadly categorized based on their purpose.
• String Functions: Manipulate string data. Examples include:
  • strlen(): Returns the length of a string.

  <?php
  $text = "Hello World";
  echo strlen($text); // Output: 11
  ?>

  • str_replace(): Replaces all occurrences of a substring with another substring.

  <?php
  $original = "The quick brown fox";
  $new = str_replace("brown", "red", $original);
  echo $new; // Output: The quick red fox
  ?>

  • substr(): Extracts a part of a string.

  <?php
  $string = "Hello";
  echo substr($string, 1, 3); // Output: ell
  ?>

• Array Functions: Work with arrays. Examples include:
  • count(): Returns the number of elements in an array.

  <?php
  $fruits = array("apple", "banana", "cherry");
  echo count($fruits); // Output: 3
  ?>

  • implode(): Joins array elements into a string.

  <?php
  $array = array("Hello", "World");
  $text = implode(" ", $array);
  echo $text; // Output: Hello World
  ?>

  • sort(): Sorts an array in ascending order.

  <?php
  $numbers = array(4, 6, 2, 22);
  sort($numbers);
  print_r($numbers); // Output: Array ( [0] => 2 [1] => 4 [2] => 6 [3] => 22 )
  ?>

• Mathematical Functions: Perform mathematical operations. Examples include:
  • abs(): Returns the absolute value of a number.

  <?php
  echo abs(-4.7); // Output: 4.7
  ?>

  • sqrt(): Returns the square root of a number.

  <?php
  echo sqrt(9);
  ?>

  • round(): Rounds a floating-point number.

  <?php
  echo round(3.14159, 2); // Output: 3.14
  ?>

• Date and Time Functions: Handle dates and times. Examples include:
  • date(): Formats a local date and time.

  <?php
  echo date("Y-m-d H:i:s"); // Output: e.g., 2024-05-15 10:30:00
  ?>

  • time(): Returns the current Unix timestamp.

  <?php
  echo time(); // Output: current Unix timestamp
  ?>

• File Handling Functions: Interact with the file system. Examples include:
  • fopen(): Opens a file or URL.
  • fclose(): Closes an open file pointer.
  • fread(): Reads from an open file.

  <?php
  $file = fopen("test.txt", "r");
  if ($file) {
      $content = fread($file, filesize("test.txt"));
      echo $content;
      fclose($file);
  }
  ?>

• Database Functions (e.g., MySQLi): Interact with databases. Examples include:
  • mysqli_connect(): Establishes a new connection to a MySQL database.
  • mysqli_query(): Performs a query on the database.
  • mysqli_fetch_assoc(): Fetches a result row as an associative array.

  <?php
  $conn = mysqli_connect("localhost", "username", "password", "database");
  if (!$conn) {
      die("Connection failed: " . mysqli_connect_error());
  }
  $sql = "SELECT id, name FROM users";
  $result = mysqli_query($conn, $sql);
  if (mysqli_num_rows($result) > 0) {
      while($row = mysqli_fetch_assoc($result)) {
          echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
      }
  } else {
      echo "0 results";
  }
  mysqli_close($conn);
  ?>

• These are just a few examples, and PHP provides many more functions for various tasks like form handling, session management, object-oriented programming, and more. Understanding and utilizing these functions is crucial for efficient web development in PHP.

Write a PHP script for searching for a web page.

Marks: 7

Searching for a web page typically involves fetching the content of a given URL and then performing a search within that content. PHP can achieve this using functions like file_get_contents() or cURL to retrieve the page content, and then string manipulation functions to find the desired keyword.

Here's a PHP script that demonstrates how to search for a keyword on a specific web page:

<?php

// Function to search for a keyword on a given URL
function searchWebPage($url, $keyword) {
    // Use file_get_contents to fetch the HTML content of the URL
    // @ suppresses warnings if the URL is not accessible
    $htmlContent = @file_get_contents($url);

    if ($htmlContent === FALSE) {
        return "<p style='color:red'>Error: Could not retrieve content from URL: " . htmlspecialchars($url) . "</p>";
    }

    // Use stripos to find the position of the keyword (case-insensitive)
    // stripos returns the position of the first occurrence of a substring in a string, case-insensitive.
    // It returns FALSE if the keyword is not found.
    $position = stripos($htmlContent, $keyword);

    if ($position !== FALSE) {
        // Keyword found
        return "<p style='color:green'>Keyword '<b>" . htmlspecialchars($keyword) . "</b>' found on page '<b>" . htmlspecialchars($url) . "</b>' at position " . ($position + 1) . ".</p>";
    } else {
        // Keyword not found
        return "<p style='color:orange'>Keyword '<b>" . htmlspecialchars($keyword) . "</b>' not found on page '<b>" . htmlspecialchars($url) . "</b>'.</p>";
    }
}

// --- Example Usage ---

// Define the URL to search and the keyword
$targetUrl = "https://www.example.com"; // Replace with the actual URL
$searchKeyword = "Example"; // Replace with the keyword you want to search for

// Call the function and display the result
echo searchWebPage($targetUrl, $searchKeyword);

// Another example with a different keyword
$searchKeyword2 = "NonExistentKeyword";
echo searchWebPage($targetUrl, $searchKeyword2);

// Example with a potentially problematic URL (for testing error handling)
$badUrl = "http://thisisnotavalidurl12345.com";
$keywordForBadUrl = "test";
echo searchWebPage($badUrl, $keywordForBadUrl);

?>

Explanation:

• searchWebPage($url, $keyword) function: This function encapsulates the logic for searching. It takes the URL and the keyword as parameters.
• @file_get_contents($url): This is the core function used to fetch the entire content of the web page into a string. The '@' symbol is used to suppress any potential warnings or errors if the URL is invalid or inaccessible, allowing us to handle errors gracefully.
• Error Handling: The script checks if file_get_contents() returned FALSE, which indicates a failure to retrieve the page content. If an error occurs, an informative message is returned.
• stripos($htmlContent, $keyword): This function searches for the first occurrence of the $keyword within the $htmlContent string. It is case-insensitive, meaning it will find "Example", "example", or "EXAMPLE". It returns the starting position (index) of the keyword if found, or FALSE if not found.
• Result Output: Based on whether the keyword was found ($position !== FALSE), the script returns a user-friendly message indicating success or failure, along with the URL and the keyword.
• htmlspecialchars(): This function is used to prevent cross-site scripting (XSS) vulnerabilities by converting special characters into HTML entities. It's good practice to use this when displaying user-provided or external data.

Note: This script performs a simple text search. For more complex web scraping or searching (e.g., searching within specific HTML tags, handling JavaScript-rendered content, or dealing with large amounts of data), more advanced techniques like using cURL with options for headers and timeouts, or employing dedicated scraping libraries, might be necessary.