Recursive Functions are functions that auto-call themself. Generally, a recursive function returns a value that are passed as argument, so the value is passed from an auto-call to the other, until it is returned.
Recursive functions are very useful in equations with factorial numbers and some operatios with multi-dimensional array.
Factorials are written like 6! and this means: 6 * 5 * 4 * 3 * 2 * 1. So 6! is 4320 and 4! is 24.
In the fallowing example we have a recursive function that finds the factorial of a number "$nr" (here 8).

// this function auto-calls itself (decrementing $nr) until $nr is 0
function factorial($nr) {
 if($nr > 0) $re = $nr * factorial($nr-1);
 else if($nr == 0) $re = 1;

 return $re;

echo '8 factorial is: '. factorial(8); // 8 factorial is: 45360

- To see another example, visit this page: Get all the unique numbers from two-dimensional array.

Daily Test with Code Example

Which HTML5 tag is indicated to be used as container for menu with navigation links in Web site?
<section> <nav> <article>
 <li><a href="" title="CSS Course">CSS Course</a></li>
 <li><a href="" title="Flash Games">Flash Games</a></li>
Which CSS property shifts an item horizontally to the left or right of where it was?
text-align clear float
.some_class {
  width: 30%;
  float: left;
Click on the Math object method which returns x, rounded downwards to the nearest integer.
Math.ceil(x) Math.abs(x) Math.floor(x)
var num = 12.34567;
num = Math.floor(num);
alert(num);       // 12
Indicate the PHP function which returns the number of characters in string.
mb_strlen() count() stristr()
$str = "string with utf-8 chars åèö";
$nrchr = mb_strlen($str);
echo $nrchr;        // 30
Recursive Functions in PHP

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