Short overview on Unit-III

 

📘 Unit – III: Working with PHP Arrays and Functions

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3a. Steps to Use Different Types of Array in a Given Application

🔹 What is an Array?

• An array stores multiple values in a single variable.

• Declared using array() or short syntax [].

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Types of Arrays in PHP

1. Indexed Array

• Elements are stored with numeric indexes (0, 1, 2…).

• Example:

<?php
$fruits = array("Apple", "Banana", "Mango");
echo $fruits[0];   // Apple
?>

✅ Steps to use in application:

1. Declare array with values.

2. Access elements by index.

3. Use for or foreach loop to process values.

Example (display all fruits):

foreach($fruits as $f){
    echo $f."<br>";
}

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2. Associative Array

• Uses key-value pairs instead of numeric index.

• Example:

<?php
$marks = array("Jay" => 85, "Deep" => 90, "Amit" => 78);
echo $marks["Deep"]; // 90
?>

✅ Steps to use:

1. Declare associative array with keys.

2. Access value using its key.

3. Loop with foreach($array as $key => $value).

Example:

foreach($marks as $name => $score){
    echo "$name scored $score <br>";
}

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3. Multidimensional Array

• Array of arrays (table-like data).

• Example:

<?php
$students = array(
    array("Jay", 21, "A"),
    array("Deep", 22, "B"),
    array("Amit", 20, "A")
);
echo $students[1][0]; // Deep
?>

✅ Steps to use:

1. Create nested arrays.

2. Access values using row & column index.

3. Use nested loops to display data.

Example (display all students):

foreach($students as $stu){
    echo $stu[0]." - Age: ".$stu[1]." - Grade: ".$stu[2]."<br>";
}

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📌 Application Example: Student Marks Application

• Indexed Array: Store subject names.

• Associative Array: Store student names with marks.

• Multidimensional Array: Store multiple students with their marks in different subjects.

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3b. Steps to Create User-Defined Functions & Work with Built-in Functions

🔹 Functions in PHP

• A function is a block of code that can be reused.

• Two types:

  1. User-defined functions

  2. Built-in functions

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1. User-Defined Functions

✅ Steps to create:

1. Declare function using function keyword.

2. Write code inside it.

3. Call function when needed.

Example 1: Simple Function

<?php
function greet(){
    echo "Welcome to PHP Functions!";
}
greet(); // Calling function
?>

Example 2: Function with Parameters

function add($a, $b){
    return $a + $b;
}
echo add(10, 20); // Output: 30

Example 3: Function with Default Argument

function greetUser($name="Guest"){
    echo "Hello, $name!";
}
greetUser("Jay"); // Hello, Jay!
greetUser();      // Hello, Guest!

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2. Built-in Functions in PHP

PHP has 1000+ built-in functions. Categories:

(a) String Functions

• strlen($str) → length of string

• strtoupper($str) → converts to uppercase

• strtolower($str) → converts to lowercase

• substr($str, start, length) → substring

Example:

$name = "php tutorial";
echo strtoupper($name); // PHP TUTORIAL

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(b) Array Functions

• count($arr) → number of elements

• sort($arr) → sort ascending

• rsort($arr) → sort descending

• array_merge($a1, $a2) → combine arrays

Example:

$fruits = ["Mango", "Apple", "Banana"];
sort($fruits);
print_r($fruits);

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(c) Math Functions

• abs(-7) → 7

• pow(2,3) → 8

• sqrt(16) → 4

• rand(1,100) → random number

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(d) Date & Time Functions

• date("Y-m-d") → 2025-08-18

• date("H:i:s") → 14:55:22

Example:

echo "Today is ".date("l"); // Outputs day of week

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(e) Other Useful Functions

• isset($var) → checks if variable exists

• empty($var) → checks if empty

• include() / require() → include external PHP file

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📌 Application Example: Online Student Report

1. Store marks in arrays.

2. Create user-defined function calculateAverage($marks).

3. Use built-in functions like count() for number of subjects, max() to find highest marks.

4. Display report using arrays + functions.

Example:

<?php
function calculateAverage($marks){
    return array_sum($marks) / count($marks);
}

$student = array("Math"=>80, "Science"=>90, "English"=>85);

echo "Average: ".calculateAverage($student);
echo "<br> Highest Marks: ".max($student);
?>

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✅ That covers Unit–III: Arrays & Functions in PHP.

Would you like me to also prepare MCQs + 3–4 marks questions with answers + diagram-based short notes PDF for Unit–III (like we did for Unit–II)?

✅ 1. Multiple Choice Questions (MCQ)

Q1. Which function returns the total number of elements in an array?
a) size()
b) count()
c) length()
d) sizeof()
👉 Answer: b) count()

Q2. Which type of array uses keys instead of numeric indexes?
a) Indexed Array
b) Associative Array
c) Multidimensional Array
d) None
👉 Answer: b) Associative Array

Q3. Which of the following is correct for defining a PHP function?
a) function myFunc{}
b) def myFunc()
c) function myFunc(){}
d) func myFunc(){}
👉 Answer: c) function myFunc(){}

Q4. Which built-in function is used to merge two arrays?
a) array_combine()
b) array_merge()
c) merge_array()
d) join_array()
👉 Answer: b) array_merge()

Q5. PHP arrays start with which index by default?
a) 0
b) 1
c) -1
d) Random
👉 Answer: a) 0

Q6. Which of these is a multidimensional array?
a) $a = array(10,20,30);
b) $a = array("x"=>1,"y"=>2);
c) $a = array(array(1,2), array(3,4));
d) $a = array(“A”, “B”, “C”);
👉 Answer: c) array(array(1,2), array(3,4))

Q7. Which function is used to check if a variable is empty?
a) isset()
b) check()
c) empty()
d) is_null()
👉 Answer: c) empty()

Q8. Which function returns the length of a string?
a) strlen()
b) length()
c) strsize()
d) count()
👉 Answer: a) strlen()

Q9. Which of the following functions returns the largest number from an array?
a) max()
b) largest()
c) big()
d) maximum()
👉 Answer: a) max()

Q10. Which loop is most commonly used to traverse arrays in PHP?
a) for
b) foreach
c) while
d) do-while
👉 Answer: b) foreach

Q11. What is the default return value of a function in PHP if no return is specified?
a) 0
b) NULL
c) False
d) Undefined
👉 Answer: b) NULL

Q12. Which function is used to generate a random number in PHP?
a) rand()
b) random()
c) shuffle()
d) gen_random()
👉 Answer: a) rand()

Q13. Which symbol is used to define variables in PHP?
a) #
b) @
c) $
d) &
👉 Answer: c) $

Q14. Which built-in function is used to convert a string to lowercase?
a) strtolower()
b) strlower()
c) lower()
d) toLower()
👉 Answer: a) strtolower()

Q15. PHP function names are:
a) Case-sensitive
b) Not case-sensitive
c) Always uppercase
d) Always lowercase
👉 Answer: b) Not case-sensitive

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✅ 2. 3–4 Marks Questions with Answers

Q1. Explain the difference between Indexed, Associative, and Multidimensional arrays in PHP with examples.
👉 Indexed arrays use numeric indexes, Associative arrays use named keys, and Multidimensional arrays are arrays inside arrays. Example:

$indexed = ["Red", "Green", "Blue"];
$assoc = ["Math"=>90, "Science"=>85];
$multi = [["Amit",21], ["Deep",22]];

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Q2. Write the steps to create and call a user-defined function in PHP.
👉 Steps:

1. Use function keyword.

2. Write function name and code block.

3. Call function using its name.

Example:

function greet($name){
   echo "Hello $name!";
}
greet("Jay");

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Q3. Describe any four string functions in PHP with examples.

• strlen("PHP") → 3

• strtoupper("php") → "PHP"

• strtolower("HELLO") → "hello"

• substr("HelloWorld",0,5) → "Hello"

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Q4. Differentiate between User-defined and Built-in functions in PHP.

• User-defined: Written by programmer, reusable, e.g., function add($a,$b){ return $a+$b; }

• Built-in: Predefined in PHP, e.g., count(), strlen(), rand()

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Q5. Explain with example how to use foreach loop to traverse an associative array.
👉 Example:

$marks = ["Jay"=>85,"Deep"=>90];
foreach($marks as $name=>$score){
   echo "$name scored $score <br>";
}

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Q6. Write steps to calculate average marks using arrays and functions.
👉 Steps:

1. Store marks in associative array.

2. Create function to calculate average using array_sum() and count().

3. Display result.

Example:

function avg($marks){
  return array_sum($marks)/count($marks);
}

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Q7. Explain the use of isset() and empty() with examples.

• isset($var) → checks if variable exists.

• empty($var) → checks if variable has no value.

Example:

$x = "";
echo isset($x);   // true
echo empty($x);   // true