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).

<?php
// 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

HTML
CSS
JavaScript
PHP-MySQL
Which tag is a block element?
<div> <img> <span>
<div>Web Programming and Development</div>
Which CSS code displays the text underlined?
font-style: italic; text-decoration: underline; font-weight: 500;
h2 {
  text-decoration: underline;
}
Click on the JavaScript function that can access other function after a specified time.
insertBefore() setTimeout() querySelector()
function someFunction() { alert("CoursesWeb.net"); }
setTimeout("someFunction()", 2000);
Click on the instruction that returns the number of items of a multidimensional array in PHP.
count($array) count($array, 1) strlen()
$food =["fruits" =>["banana", "apple"), "veggie" =>["collard", "pea"));
$nr_food = count($food, 1);
echo $nr_food;       // 6
Recursive Functions in PHP

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