If-Else, Foreach, Do-While, and While Explained with Advanced Examples

PHP, a versatile and widely-used scripting language, offers various control structures that allow developers to control the flow of their programs. In this article, we’ll explore four fundamental PHP control structures: if-else, foreach, do-while, and while. We’ll cover the basics and provide advanced examples to help you gain a deep understanding of how these structures work in real-world scenarios.

1) If-Else Statements

$temperature = 25;

if ($temperature > 30) {
    echo "It's hot outside!";
} else {
    echo "It's not too hot today.";
}

Advanced Example: User Authentication

$user_authenticated = false;

if ($user_authenticated) {
    echo "Welcome, user!";
} else {
    header("Location: login.php");
    exit;
}

In this example, the if-else statement determines whether a user is authenticated. If authenticated, they are welcomed; otherwise, they are redirected to the login page.

2) Foreach Loop

The foreach loop is a handy control structure used for iterating through arrays and objects. It simplifies the process of looping through each element without explicitly managing an index.

$fruits = ["apple", "banana", "cherry"];

foreach ($fruits as $fruit) 
    echo $fruit . " ";
}

Advanced Example: Database Query Results

$database_results = [
    ["id" => 1, "name" => "John"],
    ["id" => 2, "name" => "Jane"],
    // ...
];

foreach ($database_results as $result) {
    echo "User ID: " . $result["id"] . ", Name: " . $result["name"] . "<br>";
}

Here, the foreach loop is used to iterate through a list of database query results and display user information.

3) Do-While Loop

The do-while loop is used to repeatedly execute a block of code while a condition is true. Unlike the while loop, the do-while loop guarantees that the code block is executed at least once.

$count = 1;

do {
    echo "Count: " . $count . "<br>";
    $count++;
} while ($count <= 5);

Advanced Example: User Input Validation

do {
    $user_input = readline("Enter a positive number: ");
} while (!is_numeric($user_input) || $user_input <= 0);

echo "You entered a valid positive number: " . $user_input;

In this example, the do-while loop is used to repeatedly prompt the user for input until they enter a valid positive number.

3) While Loop

The while loop executes a block of code as long as a specified condition is true. Unlike the do-while loop, the while loop may not execute the code block at all if the condition is initially false.

$count = 1;

while ($count <= 5) {
    echo "Count: " . $count . "<br>";
    $count++;
}

Advanced Example: File Processing

$file = fopen("data.txt", "r");

while (($line = fgets($file)) !== false) {
    echo "Line from file: " . $line;
}

fclose($file);

This example demonstrates how to use a while loop to read lines from a text file until the end of the file is reached.

Conclusion

Understanding control structures like if-else, foreach, do-while, and while is crucial for any PHP developer. They empower you to make decisions, process data efficiently, and create dynamic and interactive applications. By mastering these control structures and exploring advanced examples, you can take your PHP coding skills to the next level and build robust, feature-rich applications.