The following program in PHP using recursion can be used for fibonacci series using -

<?php  

$num = 0;  

$n1 = 0;  

$n2 = 1;  

echo '<h3>Fibonacci series for first 12 numbers: </h3>';  

echo '\n';  

echo $n1.' '.$n2.' ';  

while ($num < 10 )  

{  

  $n3 = $n2 + $n1;  

  echo $n3.' ';  

  $n1 = $n2;  

 $n2 = $n3; 

    $num = $num + 1;  

   ?>  

Here is an example of a program that uses recursion to generate the Fibonacci series in PHP:

Copy code

<?php

// Function to generate Fibonacci series

function fibonacci($n) {    

if ($n <= 0) {    

    return 0;    

} else if ($n == 1) {   

     return 1;  

  } else {     

   return fibonacci($n-1) + fibonacci($n-2);    

}

}

// Test the function $n = 10;

for ($i = 0; $i < $n; $i++) {

   echo fibonacci($i) . ' ';

}

?>

The function fibonacci() uses recursion to calculate the Fibonacci series. The base case of the recursion is when the input $n is 0 or 1, in which case the function returns 0 or 1 respectively. For any other value of $n, the function calls itself twice, with the input decremented by 1 and 2, respectively. The value returned by the function is the sum of the two recursive calls.

In this program, the function is called in a for loop, where the input $i varies from 0 to $n-1. This will generate and print the first $n numbers of Fibonacci series.

You can also create a function that returns an array with the Fibonacci series or you can modify the above program to print the fibonacci series up to a certain number, not a quantity of numbers.

The program to generate the fibonacci series is as follows:

• <?php  

<?php  

/* Print fiboancci series upto 12 elements. */  

$num = 12;  

echo '<h3>Fibonacci series using recursive function:</h3>';  

echo '\n';  

/* Recursive function for fibonacci series. */  

function series($num){  

    if($num == 0){  

    return 0;  

    }else if( $num == 1){  

return 1;  

} else {  

return (series($num-1) + series($num-2));  

}   

}  

/* Call Function. */  

for ($i = 0; $i < $num; $i++){  

echo series($i);  

echo '\n';  

}