<?php
function generate_rand_array($a,$b)
{
    $z = [];
    for ($i = $a;$i<=$b+1;$i++) {
        $z[$i] = rand($a,$b);
    }

    return $z;
}
$n = rand(1,100);
$a = generate_rand_array(1,$n);
print_r($a);
for($p = 1;$p <= $n+1;$p++)
{
    if ($a[ $p ] > $n) {
        $z = $a[ $p ] - $n;
    } else {
        $z = $a[ $p ];
    }
    if ($a[ $z ] > $n) {
        echo $p . ' пиймав на вила' . "\n";
    } else {
        $a[ $z ] = $a[ $z ] + $n;
    }
}