$bank = array();
$players = 100;
$rounds = 5000;

for ($i = 0; $i<$players; $i++) {
    //setup coins
    $bank[$i] = 100;
}

for ($j=1;$j<$rounds;$j++){

    for ($i = 0; $i<$players; $i++) {
        //take coin
        if($bank[$i]>0) {
            $bank[$i] = $bank[$i] - 1;
        }
        //random select
        $victim = rand(0,$players-1);
        //give coin
        $bank[$victim] = $bank[$victim]+1;
    }

}