Function declaration and calling in PHP - Mini Project: Build & Apply

Function declaration and calling

📖 Scenario: You are creating a simple PHP program to greet users by their name. This is like writing a small helper that says hello whenever you ask it.

🎯 Goal: Build a PHP program that declares a function called greet which takes a name and returns a greeting message. Then call this function with a specific name and print the greeting.

📋 What You'll Learn

Declare a function named greet that accepts one parameter called name.

The function should return a string greeting in the format: "Hello, {name}!".

Call the greet function with the argument "Alice".

Print the result of the function call.

💡 Why This Matters

🌍 Real World

Functions help organize code into reusable blocks, like helpers that do one job well. This is common in all programming tasks.

💼 Career

Knowing how to declare and call functions is essential for any PHP developer to write clean, maintainable code.

1

Declare the greet function

Write a PHP function declaration named greet that takes one parameter called name. Inside the function, return the string "Hello, " concatenated with the name parameter and an exclamation mark "!".

PHP

<?php

// Declare the function greet with parameter name
// Your code here

Hint

Use the function keyword, then the function name greet, and parentheses with $name inside. Use return to send back the greeting string.

2

Call the greet function with "Alice"

Create a variable called message and set it to the result of calling the greet function with the argument "Alice".

PHP

<?php

function greet($name) {
    return "Hello, " . $name . "!";
}

// Call greet with "Alice" and store in message
// Your code here

Hint

Assign the result of greet("Alice") to the variable $message.

3

Print the greeting message

Use echo to print the variable message.

PHP

<?php

function greet($name) {
    return "Hello, " . $name . "!";
}

$message = greet("Alice");

// Print the message
// Your code here

Hint

Use echo $message; to display the greeting on the screen.

4

Run the program and see the output

Run the PHP script and observe the output. It should print Hello, Alice! exactly.

PHP

<?php

function greet($name) {
    return "Hello, " . $name . "!";
}

$message = greet("Alice");
echo $message;

// Run the script to see output
// Your code here

Hint

Make sure you run the PHP file in a server or command line to see the output.

Practice

1. What is the correct way to declare a function named greet in PHP?

easy

A. function greet() { }

B. def greet() { }

C. func greet() { }

D. function: greet() { }

Solution

1. Step 1: Recognize PHP function declaration syntax

   In PHP, functions are declared using the keyword function followed by the function name and parentheses.

2. Step 2: Match the correct syntax

   function greet() { } uses function greet() { }, which is the correct PHP syntax for declaring a function named greet.

3. Final Answer:

   function greet() { } -> Option A

4. Quick Check:

   PHP function declaration = function greet() { } [OK]

Hint: Use 'function' keyword to declare functions in PHP [OK]

Common Mistakes:

• Using 'def' instead of 'function'
• Adding a colon after 'function'
• Using 'func' keyword which is not valid in PHP

2. Which of the following is the correct way to call a function named sayHello in PHP?

easy

A. call sayHello();

B. sayHello();

C. sayHello;

D. callFunction(sayHello);

Solution

1. Step 1: Understand PHP function call syntax

   In PHP, to call a function, you write the function name followed by parentheses, optionally with arguments inside.

2. Step 2: Identify the correct option

   sayHello(); uses sayHello();, which is the correct way to call the function named sayHello.

3. Final Answer:

   sayHello(); -> Option B

4. Quick Check:

   Function call syntax = sayHello(); [OK]

Hint: Call functions by name with parentheses () [OK]

Common Mistakes:

• Using 'call' keyword which does not exist in PHP
• Omitting parentheses when calling functions
• Using incorrect function call syntax like callFunction()

3. What will be the output of the following PHP code?

function add($a, $b) {
    return $a + $b;
}
echo add(3, 4);

medium

A. 7

B. 34

C. add(3, 4)

D. Error

Solution

1. Step 1: Understand the function behavior

   The function add takes two parameters and returns their sum.

2. Step 2: Calculate the return value

   Calling add(3, 4) returns 3 + 4 = 7, which is then printed by echo.

3. Final Answer:

   7 -> Option A

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Functions return values; echo prints the result [OK]

Common Mistakes:

• Concatenating numbers as strings instead of adding
• Expecting function name to print instead of return value
• Syntax errors from missing semicolons

4. Identify the error in the following PHP code:

function greet() {
    echo "Hello!";
}
greet;

medium

A. Missing semicolon after function declaration

B. Function name is incorrect

C. Missing parentheses when calling the function

D. Echo statement syntax error

Solution

1. Step 1: Check function call syntax

   The function greet is declared correctly, but when calling it, parentheses are missing.

2. Step 2: Understand PHP function call requirements

   In PHP, functions must be called with parentheses, even if they take no arguments. So greet; is invalid; it should be greet();.

3. Final Answer:

   Missing parentheses when calling the function -> Option C

4. Quick Check:

   Function calls need () even if no arguments [OK]

Hint: Always use () to call functions, even if empty [OK]

Common Mistakes:

• Calling functions without parentheses
• Confusing function declaration with call
• Missing semicolons elsewhere

5. Consider the following PHP code:

function multiply($x, $y = 2) {
    return $x * $y;
}
echo multiply(5);

What will be the output and why?

hard

A. 0 because default value is ignored

B. 5 because only one argument is passed

C. Error because both parameters are required

D. 10 because the second parameter uses default value 2

Solution

1. Step 1: Understand default parameter usage

   The function multiply has two parameters, where $y has a default value of 2.

2. Step 2: Analyze the function call

   Calling multiply(5) passes 5 as $x, and since $y is not provided, it uses the default 2.

3. Step 3: Calculate the result

   The function returns 5 * 2 = 10, which is printed by echo.

4. Final Answer:

   10 because the second parameter uses default value 2 -> Option D

5. Quick Check:

   5 * 2 = 10 with default parameter [OK]

Hint: Default parameters fill missing arguments automatically [OK]

Common Mistakes:

• Assuming all parameters must be passed
• Ignoring default values
• Expecting error when missing arguments