Nested recursive function is throwing an error [duplicate] - php

Question

This question already has answers here:
"Fatal error: Cannot redeclare <function>"
(18 answers)
Closed 2 years ago.
I have a nested recursive function it's a task from codewars.
persistence(39) === 3; // because 3 * 9 = 27, 2 * 7 = 14, 1 * 4 = 4
and 4 has only one digit persistence(999) === 4; // because 9 * 9 * 9
= 729, 7 * 2 * 9 = 126, 1 * 2 * 6 = 12, and finally 1 * 2 = 2;
persistence(4) === 0; // because 4 is already a one-digit number
which throws :
Fatal error: Cannot redeclare rec();
function persistence(int $num): int {
$str = (string)$num;
$nums = str_split($str);
$count = count($nums);
if( $count === 0 ){
return 0;
}
$x = 0;
function rec($nums, $n) {
$result = [];
for ($i = 0; $i < count($nums); ++$i) {
if ($i == 0) {
$result = $nums[$i];
} else {
$result *= $nums[$i];
}
}
$num = implode('',$nums);
$diff = $num - $result;
if ( $diff != 0 ) {
$n += 1;
$result = str_split($result,1);
return rec($result, $n);
}
return $n;
}
$result = rec($nums,$x);
return (int)$result;
}
I've tried to use an variable function
$rec = 'rec';
$result = $rec($nums,$n)
but there are another error : `
Fatal error: Cannot redeclare rec()
`
PHP 7.4 version. Can anyone explain me what the problem is ?

Answer 1

Don't define the function inside the other function:
You have:
function persistence(int $num): int {
// code ...
function rec($nums, $n) {
// code ...
}
}
This means that the function rec should be created each time the function persistence gets called.
You should define them first:
function persistence(int $num): int {
// code ...
}
function rec($nums, $n) {
// code ...
}
And then call them to your liking, for example like you already do:
$rec = 'rec';
$result = $rec($nums,$n)