Fibonacci Series

Fibonacci series is the one in which you will get your next term by adding previous two numbers.

For example,

1. 0 1 1 2 3 5 8 13 21 34  
2. Here, 0 + 1 = 1  
3.             1 + 1 = 2  
4.             3 + 2 = 5  

and so on.

Logic:

• Initializing first and second number as 0 and 1.
• Print first and second number.
• From next number, start your loop. So third number will be the sum of the first two numbers.

Example:

HTML Tutorial

We'll show an example to print the first 12 numbers of a Fibonacci series.

1. <?php  
2. $num = 0;  
3. $n1 = 0;  
4. $n2 = 1;  
5. echo "<h3>Fibonacci series for first 12 numbers: </h3>";  
6. echo "\n";  
7. echo $n1.' '.$n2.' ';  
8. while ($num < 10 )  
9. {  
10.     $n3 = $n2 + $n1;  
11.     echo $n3.' ';  
12.     $n1 = $n2;  
13.     $n2 = $n3;  
14.     $num = $num + 1;  
15. ?>  

Output:

Fibonacci series using Recursive function

Recursion is a phenomenon in which the recursion function calls itself until the base condition is reached.

1. <?php  
2. /* Print fiboancci series upto 12 elements. */  
3. $num = 12;  
4. echo "<h3>Fibonacci series using recursive function:</h3>";  
5. echo "\n";  
6. /* Recursive function for fibonacci series. */  
7. function series($num){  
8.     if($num == 0){  
9.     return 0;  
10.     }else if( $num == 1){  
11. return 1;  
12. }  else {  
13. return (series($num-1) + series($num-2));  
14. }   
15. }  
16. /* Call Function. */  
17. for ($i = 0; $i < $num; $i++){  
18. echo series($i);  
19. echo "\n";  
20. }  

Output: