Fibonacci Series

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

For example,

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

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

<?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;
?>

Output:

Fibonacci series using Recursive function

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

<?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";
}

Output: