Control Structures: If, Else, and Switch in PHP

1. Introduction

Goal of the Tutorial

This tutorial aims to provide an understanding of the 'if', 'else', and 'switch' control structures in PHP. These are fundamental components for controlling the flow of a PHP script based on different conditions.

Learning Outcomes

By the end of this tutorial, you will be able to:
- Understand and use 'if', 'else', and 'switch' control structures in PHP.
- Write PHP scripts that react differently to different conditions.

Prerequisites

A basic understanding of PHP and its syntax is required. Familiarity with the concepts of variables and data types in PHP will be beneficial.

2. Step-by-Step Guide

'If' Control Structure

The 'if' control structure is used to execute a block of code if a specified condition is true.

if (condition) {
  // code to be executed if the condition is true
}

'Else' Control Structure

The 'else' control structure is used to execute a block of code if the same condition is false.

if (condition) {
  // code to be executed if the condition is true
} else {
  // code to be executed if the condition is false
}

'Elseif' Control Structure

The 'elseif' control structure is a combination of 'if' and 'else'. It can be used to add more conditions.

if (condition1) {
  // code to be executed if condition1 is true
} elseif (condition2) {
  // code to be executed if condition1 is false and condition2 is true
} else {
  // code to be executed if both condition1 and condition2 are false
}

'Switch' Control Structure

The 'switch' control structure is used to select one of many blocks of code to be executed.

switch (n) {
  case label1:
    // code to be executed if n=label1
    break;
  case label2:
    // code to be executed if n=label2
    break;
  default:
    // code to be executed if n is different from both label1 and label2
}

3. Code Examples

'If' Control Structure Example

$age = 20;
if ($age >= 18) {
  echo "You are eligible to vote.";
}

In this example, if the age is greater than or equal to 18, the message "You are eligible to vote." will be printed.

'If-Else' Control Structure Example

$age = 15;
if ($age >= 18) {
  echo "You are eligible to vote.";
} else {
  echo "You are not eligible to vote.";
}

In this example, if the age is less than 18, the message "You are not eligible to vote." will be printed.

'If-Elseif-Else' Control Structure Example

$score = 85;
if ($score > 90) {
  echo "Excellent score!";
} elseif ($score > 70) {
  echo "Good score!";
} else {
  echo "Try harder!";
}

In this example, if the score is greater than 70 but less than or equal to 90, the message "Good score!" will be printed.

'Switch' Control Structure Example

$day = "Mon";
switch ($day) {
  case "Mon":
    echo "Today is Monday.";
    break;
  case "Tue":
    echo "Today is Tuesday.";
    break;
  default:
    echo "Invalid day.";
}

In this example, if $day is "Mon", the message "Today is Monday." will be printed.

4. Summary

In this tutorial, we covered the 'if', 'else', and 'switch' control structures in PHP, how to use them, and their syntax. We also looked at practical examples of each control structure.

Continue your PHP learning journey by exploring more advanced control structures, such as loops and functions.

5. Practice Exercises

1. Write a PHP script that determines whether a number is positive, negative, or zero using 'if-else' control structure.
2. Write a PHP script that determines the grade of a student based on a score using 'if-elseif-else' control structure.
3. Write a PHP script that prints the name of a day based on its numeric representation (1 for Monday, 2 for Tuesday, and so on) using 'switch' control structure.

Tips for further practice

• Create more complex conditions using logical operators.
• Use nested 'if' and 'switch' statements.