PHP Function and Array Exercise Solutions | KalviGavani

Chapter 5 — PHP Function and Array: Exercise Solutions Guide

How to Use This Page

1. Attempt every exercise question on your own first — use your Samacheer Kalvi textbook and class notes. 2. Compare your answers with the solutions below only after you have written your own. 3. Read the explanations for MCQs and True/False items — understanding why an answer is correct is more important than the answer itself. 4. Practise the short and detailed answers by writing them in your own words; do not memorise verbatim. 5. Use the Exam Checklist at the end for a quick pre-exam revision round.

Key Concepts (Quick Recap)

• A function is a reusable block of code that performs a specific task; it improves code organisation and reduces repetition.
• Built-in functions are pre-defined in PHP (e.g., strlen(), count(), array_push()); user-defined functions are created by the programmer using the function keyword.
• User-defined functions: function functionName($param1, $param2) { ... return $result; }
• Functions can have parameters (inputs) and a return value (output); both are optional.
• Default parameters assign a default value when no argument is passed: function greet($name = "Guest") { ... }
• An array is a special variable that can hold multiple values in a single variable.
• Indexed arrays use numeric keys starting from 0: $colors = array("Red", "Green", "Blue");
• Associative arrays use named keys: $student = array("name" => "Arun", "age" => 20);
• Multidimensional arrays contain other arrays as elements: $marks = array(array(85, 90), array(78, 88));
• Common array functions: count(), sort(), array_push(), array_pop(), array_merge(), in_array(), array_keys(), array_values()
• Common string functions: strlen(), strtoupper(), strtolower(), substr(), str_replace(), strpos(), explode(), implode()
• The return statement sends a value back to the calling code and exits the function.

I. Choose the Best Answer (MCQs)

1. Which keyword is used to define a user-defined function in PHP? (a) def (b) func (c) function (d) define

2. What is the output of count($arr) where $arr = array(10, 20, 30, 40, 50);? (a) 4 (b) 5 (c) 50 (d) 10

3. Which function is used to find the length of a string in PHP? (a) strlength() (b) strlen() (c) length() (d) sizeof()

4. In an indexed array, the first element has an index of: (a) 1 (b) 0 (c) -1 (d) null

5. Which of the following creates an associative array? (a) $arr = array(10, 20, 30); (b) $arr = array("a" => 10, "b" => 20); (c) $arr = [1, 2, 3]; (d) $arr = "Hello";

6. Which function adds an element to the end of an array? (a) array_pop() (b) array_push() (c) array_shift() (d) array_unshift()

7. What does the return statement do in a function? (a) Prints output to the browser (b) Sends a value back to the calling code and exits the function (c) Declares a variable (d) Loops through an array

8. What will strtoupper("hello") return? (a) "hello" (b) "HELLO" (c) "Hello" (d) Error

9. Which function converts a string to an array by splitting it on a delimiter? (a) implode() (b) explode() (c) split() (d) join()

10. What does array_merge($arr1, $arr2) do? (a) Sorts both arrays (b) Removes duplicates from both arrays (c) Combines two arrays into one (d) Finds common elements

II. Fill in the Blanks

1. The keyword used to define a user-defined function in PHP is function. 2. The return statement sends a value back from a function to the calling code. 3. In an indexed array, the first element has an index of 0. 4. The count() function returns the number of elements in an array. 5. An associative array uses named keys instead of numeric indices. 6. The strlen() function returns the length of a string. 7. The explode() function splits a string into an array based on a delimiter. 8. The implode() function joins array elements into a string. 9. The array_push() function adds elements to the end of an array. 10. A multidimensional array is an array that contains one or more arrays as its elements.

III. True or False

IV. Match the Following

Set A

Set B

V. Short Answer Questions

function functionName($parameter1, $parameter2) {
    // Function body
    return $result;
}

<?php
  // Function definition
  function add($a, $b) {
      $sum = $a + $b;
      return $sum;
  }

  // Function call
  $result = add(10, 20);
  echo "Sum = " . $result;  // Output: Sum = 30
?>

<?php
  function greet($name = "Guest") {
      echo "Hello, " . $name . "!";
  }

  greet("Arun");    // Output: Hello, Arun!
  greet();          // Output: Hello, Guest!
?>

<?php
  function displayMessage() {
      echo "Welcome to PHP!";
  }

  displayMessage();  // Output: Welcome to PHP!
?>

<?php
  // Using array()
  $colors = array("Red", "Green", "Blue");
  echo $colors[0];  // Output: Red
  echo $colors[1];  // Output: Green

  // Using short syntax
  $numbers = [10, 20, 30, 40];
  echo $numbers[2];  // Output: 30
?>

<?php
  $student = array(
      "name" => "Arun",
      "age" => 20,
      "marks" => 85
  );

  echo $student["name"];   // Output: Arun
  echo $student["age"];    // Output: 20
  echo $student["marks"];  // Output: 85
?>

<?php
  $students = array(
      array("Arun", 101, 85),
      array("Bharathi", 102, 92),
      array("Chandru", 103, 78)
  );

  echo $students[0][0];  // Output: Arun
  echo $students[1][2];  // Output: 92
  echo $students[2][1];  // Output: 103
?>

<?php
  // Using echo
  function sayHello() {
      echo "Hello!";
  }
  sayHello();  // Output: Hello!

  // Using return
  function getGreeting() {
      return "Hello!";
  }
  $msg = getGreeting();  // $msg = "Hello!"
  echo $msg;             // Output: Hello!
?>

echo strlen("Hello");  // Output: 5

echo strtoupper("hello world");  // Output: HELLO WORLD

echo strtolower("HELLO WORLD");  // Output: hello world

echo substr("Hello World", 0, 5);  // Output: Hello
echo substr("Hello World", 6);      // Output: World

echo str_replace("world", "PHP", "Hello world");  // Output: Hello PHP

echo strpos("Hello World", "World");  // Output: 6

$arr = explode(",", "Red,Green,Blue");
// $arr = array("Red", "Green", "Blue")

echo implode("-", array("2026", "06", "13"));  // Output: 2026-06-13

<?php
  function sayHello() {
      echo "Hello!";
  }
  sayHello();  // Output: Hello!
?>

<?php
  function greet($name) {
      echo "Hello, " . $name . "!";
  }
  greet("Arun");      // Output: Hello, Arun!
  greet("Bharathi");  // Output: Hello, Bharathi!
?>

<?php
  function add($a, $b) {
      return $a + $b;
  }
  echo add(10, 20);  // Output: 30
  echo add(5, 7);    // Output: 12
?>

<?php
  function calculateArea($length, $width = 10) {
      return $length * $width;
  }
  echo calculateArea(5);      // Output: 50 (uses default width=10)
  echo calculateArea(5, 20); // Output: 100 (overrides default)
?>

<?php
  $numbers = array(40, 10, 30, 20);
  sort($numbers);
  print_r($numbers);  // Array([0]=>10 [1]=>20 [2]=>30 [3]=>40)
?>

<?php
  $numbers = array(10, 20, 30, 40);
  rsort($numbers);
  print_r($numbers);  // Array([0]=>40 [1]=>30 [2]=>20 [3]=>10)
?>

<?php
  $marks = array("Arun" => 85, "Bharathi" => 92, "Chandru" => 78);
  asort($marks);
  // Chandru => 78, Arun => 85, Bharathi => 92
?>

<?php
  $marks = array("Chandru" => 78, "Arun" => 85, "Bharathi" => 92);
  ksort($marks);
  // Arun => 85, Bharathi => 92, Chandru => 78
?>

<?php
  $marks = array("Arun" => 85, "Bharathi" => 92, "Chandru" => 78);
  arsort($marks);
  // Bharathi => 92, Arun => 85, Chandru => 78
?>

VI. Detailed Answer Questions

function functionName($param1, $param2, ...) {
    // Function body
    return $value;  // Optional
}

<?php
  function displayMessage() {
      echo "Welcome to KalviGavani!";
  }
  displayMessage();  // Output: Welcome to KalviGavani!
?>

<?php
  function greet($name) {
      echo "Hello, " . $name . "!";
  }
  greet("Arun");  // Output: Hello, Arun!
?>

<?php
  function add($a, $b) {
      $sum = $a + $b;
      return $sum;
  }
  $result = add(10, 20);
  echo $result;  // Output: 30
?>

<?php
  function calculateArea($length, $width = 10) {
      return $length * $width;
  }
  echo calculateArea(5);      // Output: 50 (width = 10 by default)
  echo calculateArea(5, 20);  // Output: 100 (width = 20)
?>

<?php
  function getMinMax($arr) {
      $min = min($arr);
      $max = max($arr);
      return array($min, $max);
  }
  $result = getMinMax(array(10, 5, 20, 15));
  echo "Min: " . $result[0] . ", Max: " . $result[1];
  // Output: Min: 5, Max: 20
?>

<?php
  $student = array(
      "name" => "Arun",
      "age" => 20,
      "marks" => 85
  );
?>

<?php
  $student = [
      "name" => "Arun",
      "age" => 20,
      "marks" => 85
  ];
?>

<?php
  $student["name"] = "Arun";
  $student["age"] = 20;
  $student["marks"] = 85;
?>

<?php
  echo $student["name"];   // Output: Arun
  echo $student["age"];    // Output: 20
  echo $student["marks"];  // Output: 85
?>

<?php
  $student["marks"] = 90;  // Change marks from 85 to 90
  $student["grade"] = "A"; // Add a new key-value pair
?>

<?php
  $student = array(
      "name" => "Arun",
      "age" => 20,
      "marks" => 85
  );

  foreach ($student as $key => $value) {
      echo "$key: $value <br>";
  }
  // Output:
  // name: Arun
  // age: 20
  // marks: 85
?>

<?php
  $students = array(
      "student1" => array(
          "name" => "Arun",
          "age" => 20,
          "marks" => 85
      ),
      "student2" => array(
          "name" => "Bharathi",
          "age" => 21,
          "marks" => 92
      )
  );

  echo $students["student1"]["name"];   // Output: Arun
  echo $students["student2"]["marks"];   // Output: 92
?>

<?php
  $student = array("name" => "Arun", "age" => 20, "marks" => 85);

  // Get all keys
  print_r(array_keys($student));
  // Output: Array([0]=>name [1]=>age [2]=>marks)

  // Get all values
  print_r(array_values($student));
  // Output: Array([0]=>Arun [1]=>20 [2]=>85)

  // Check if a key exists
  echo array_key_exists("name", $student);  // Output: 1 (true)

  // Remove an element
  unset($student["age"]);
?>

<?php
  $students = array(
      array("Arun", 101, 85),
      array("Bharathi", 102, 92),
      array("Chandru", 103, 78)
  );
?>

<?php
  echo $students[0][0];  // Output: Arun
  echo $students[0][1];  // Output: 101
  echo $students[1][2];  // Output: 92
  echo $students[2][0];  // Output: Chandru
?>

<?php
  $students = array(
      array("Arun", 101, 85),
      array("Bharathi", 102, 92),
      array("Chandru", 103, 78)
  );

  for ($i = 0; $i < count($students); $i++) {
      echo "Name: " . $students[$i][0] . ", ";
      echo "Roll No: " . $students[$i][1] . ", ";
      echo "Marks: " . $students[$i][2] . "<br>";
  }
  // Output:
  // Name: Arun, Roll No: 101, Marks: 85
  // Name: Bharathi, Roll No: 102, Marks: 92
  // Name: Chandru, Roll No: 103, Marks: 78
?>

<?php
  $students = array(
      "student1" => array("name" => "Arun", "marks" => 85),
      "student2" => array("name" => "Bharathi", "marks" => 92),
      "student3" => array("name" => "Chandru", "marks" => 78)
  );

  // Accessing elements
  echo $students["student1"]["name"];   // Output: Arun
  echo $students["student2"]["marks"];   // Output: 92

  // Looping with foreach
  foreach ($students as $key => $value) {
      echo "$key: " . $value["name"] . " - " . $value["marks"] . "<br>";
  }
?>

<?php
  $school = array(
      "class12" => array(
          "sectionA" => array("Arun", "Bharathi"),
          "sectionB" => array("Chandru", "Deepa")
      ),
      "class11" => array(
          "sectionA" => array("Ezhil", "Farid"),
          "sectionB" => array("Ganesh", "Hari")
      )
  );

  echo $school["class12"]["sectionA"][0];  // Output: Arun
  echo $school["class11"]["sectionB"][1];  // Output: Hari
?>

<?php
  $arr = array(10, 20, 30, 40, 50);
  echo count($arr);  // Output: 5
?>

<?php
  $numbers = array(40, 10, 30, 20);
  sort($numbers);
  print_r($numbers);  // Array([0]=>10 [1]=>20 [2]=>30 [3]=>40)
?>

<?php
  $numbers = array(10, 30, 20, 40);
  rsort($numbers);
  print_r($numbers);  // Array([0]=>40 [1]=>30 [2]=>20 [3]=>10)
?>

<?php
  $fruits = array("Apple", "Banana");
  array_push($fruits, "Cherry", "Date");
  print_r($fruits);
  // Array([0]=>Apple [1]=>Banana [2]=>Cherry [3]=>Date)
?>

<?php
  $fruits = array("Apple", "Banana", "Cherry");
  $last = array_pop($fruits);
  echo $last;  // Output: Cherry
  print_r($fruits);  // Array([0]=>Apple [1]=>Banana)
?>

<?php
  $arr1 = array("Red", "Green");
  $arr2 = array("Blue", "Yellow");
  $result = array_merge($arr1, $arr2);
  print_r($result);
  // Array([0]=>Red [1]=>Green [2]=>Blue [3]=>Yellow)
?>

<?php
  $fruits = array("Apple", "Banana", "Cherry");
  echo in_array("Banana", $fruits);  // Output: 1 (true)
  echo in_array("Grape", $fruits);    // Output:  (false)
?>

<?php
  $student = array("name" => "Arun", "age" => 20, "marks" => 85);
  print_r(array_keys($student));
  // Array([0]=>name [1]=>age [2]=>marks)
?>

<?php
  $student = array("name" => "Arun", "age" => 20, "marks" => 85);
  print_r(array_values($student));
  // Array([0]=>Arun [1]=>20 [2]=>85)
?>

<?php
  $arr = array(10, 20, 30, 40);
  $rev = array_reverse($arr);
  print_r($rev);  // Array([0]=>40 [1]=>30 [2]=>20 [3]=>10)
?>

<?php
  $marks = array("Arun" => 85, "Bharathi" => 92, "Chandru" => 78);
  asort($marks);
  foreach ($marks as $name => $score) {
      echo "$name: $score\n";
  }
  // Chandru: 78, Arun: 85, Bharathi: 92
?>

<?php
  $marks = array("Chandru" => 78, "Arun" => 85, "Bharathi" => 92);
  ksort($marks);
  foreach ($marks as $name => $score) {
      echo "$name: $score\n";
  }
  // Arun: 85, Bharathi: 92, Chandru: 78
?>

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

<?php
  echo strtoupper("hello world");  // Output: HELLO WORLD
?>

<?php
  echo strtolower("HELLO WORLD");  // Output: hello world
?>

<?php
  echo substr("Hello World", 0, 5);  // Output: Hello (start at 0, length 5)
  echo substr("Hello World", 6);      // Output: World (from position 6 to end)
  echo substr("Hello World", -5);     // Output: World (last 5 characters)
?>

<?php
  echo str_replace("world", "PHP", "Hello world");
  // Output: Hello PHP

  // Replace all occurrences
  echo str_replace("a", "o", "banana");
  // Output: bonono
?>

<?php
  echo strpos("Hello World", "World");  // Output: 6
  echo strpos("Hello World", "PHP");     // Output: (false, not found)
?>

<?php
  $str = "Red,Green,Blue,Yellow";
  $arr = explode(",", $str);
  print_r($arr);
  // Array([0]=>Red [1]=>Green [2]=>Blue [3]=>Yellow)
?>

<?php
  $arr = array("Red", "Green", "Blue");
  echo implode(" - ", $arr);  // Output: Red - Green - Blue
  echo implode("", $arr);      // Output: RedGreenBlue
?>

<?php
  $str = "  Hello World  ";
  echo trim($str);  // Output: "Hello World" (spaces removed)

  // Related functions:
  echo ltrim($str);  // Removes leading whitespace
  echo rtrim($str);  // Removes trailing whitespace
?>

<?php
  echo ucfirst("hello world");  // Output: Hello world

  // Related: ucwords() — capitalise first character of each word
  echo ucwords("hello world");  // Output: Hello World
?>

<?php
  echo strrev("Hello");  // Output: olleH
?>

<?php
  echo strcmp("apple", "banana");  // Output: negative (apple < banana)
  echo strcmp("banana", "apple");  // Output: positive (banana > apple)
  echo strcmp("apple", "apple");   // Output: 0 (strings are equal)
?>

Common Mistakes

1. Forgetting the $ before variable names — PHP requires $ for all variables. Writing name = "Arun" instead of $name = "Arun" causes a parse error.

2. Using = instead of == in conditions — if ($x = 5) assigns 5 (always true); use if ($x == 5) for comparison.

3. Confusing indexed and associative array access — $arr[0] accesses indexed arrays; $arr["name"] accesses associative arrays. Using the wrong key type causes errors.

4. Confusing echo and return in functions — echo prints output directly; return sends a value back to the calling code. Use return when the result needs further processing.

5. Forgetting semicolons after statements — Every PHP statement must end with ;. Missing semicolons cause parse errors.

6. Mixing up explode() and implode() — explode() splits a string INTO an array; implode() joins an array INTO a string. They are opposite operations.

7. Not understanding that sort() re-indexes arrays — After sort(), associative arrays lose their string keys and get re-indexed numerically. Use asort() to preserve key-value associations.

Exam Checklist

• [ ] Can define and call user-defined functions with and without parameters
• [ ] Understand function parameters, default values, and return values
• [ ] Can differentiate between indexed, associative, and multidimensional arrays
• [ ] Can create, access, and modify all three array types
• [ ] Know key array functions: count(), sort(), array_push(), array_pop(), array_merge(), in_array()
• [ ] Can use string functions: strlen(), strtoupper(), strtolower(), substr(), str_replace(), explode(), implode()
• [ ] Understand the difference between echo and return
• [ ] Can loop through arrays using for and foreach
• [ ] Know sorting functions: sort(), rsort(), asort(), ksort(), arsort()
• [ ] Can write and trace through PHP functions and arrays in exam questions