Learn PHP programming from scratch: master the implementation skills of Fibonacci sequence

Learn PHP programming from scratch: Master the implementation skills of Fibonacci sequence

Fibonacci sequence refers to such a sequence: 0 , 1, 1, 2, 3, 5, 8, 13, 21, 34... Mathematically, the Fibonacci sequence is defined in a recursive way, that is, each number is the sum of the previous two numbers. . In computer programming, the Fibonacci sequence is often used to practice algorithms and programming skills, so it is crucial for beginners to master how to implement this sequence.

PHP is a popular server-side scripting language widely used for web development. The following will introduce how to implement the Fibonacci sequence in PHP, and provide specific code examples to help readers better understand the implementation principle of the algorithm.

First, let's look at the simplest implementation: using recursion. Recursion is a technique that uses the function itself within the function definition. In the Fibonacci sequence, this can be achieved through recursion as follows:

function fibonacci($n) {
    if ($n <= 1) {
        return $n;
    }
    return fibonacci($n - 1) fibonacci($n - 2);
}

// Output the first 10 numbers of the Fibonacci sequence
for ($i = 0; $i < 10; $i ) {
    echo fibonacci($i) . " ";
}

In the above code, a function named fibonacci is defined, which accepts a parameter $n, indicating the position of the Fibonacci sequence to be calculated. If $n is less than or equal to 1, $n is returned directly. Otherwise, use a recursive call to itself to calculate the sum of the numbers in the first two positions. Finally, the first 10 numbers of the Fibonacci sequence are output through a loop.

However, although the above recursive implementation method is simple and intuitive, it is less efficient. Because the same value will be calculated repeatedly during the calculation process, resulting in multiple redundant operations. In order to improve efficiency, the Fibonacci sequence can be implemented in a loop. Here's how to implement it using a loop:

function fibonacci($n) {
    $arr = [0, 1];
    for ($i = 2; $i <= $n; $i ) {
        $arr[$i] = $arr[$i - 1] $arr[$i - 2];
    }
    return $arr;
}

// Output the first 10 numbers of the Fibonacci sequence
$result = fibonacci(9);
foreach ($result as $num) {
    echo $num . " ";
}

In the above code, a function named fibonacci is defined, which accepts a parameter $n, indicating the position of the Fibonacci sequence to be calculated. The value of each position is calculated and stored sequentially through loop iteration, which avoids repeated calculations and improves efficiency. Finally, the first 10 numbers of the Fibonacci sequence are output through a loop.

Through the comparison of the above two methods, we can find that it is more efficient to use loops to implement the Fibonacci sequence. For beginners, it is important to master the implementation principles of these two methods, which can help them better understand the concepts of recursion and loops, and learn to use them flexibly in actual programming.

I hope that through the introduction and code examples of this article, readers can have a deeper understanding of the implementation techniques of Fibonacci sequence in PHP programming, and lay a good foundation for further learning algorithms and data structures. I hope every beginner can continue to make progress on the road of programming and explore more interesting programming technologies!

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