Organise_duplicate_numbers_in_list.php

<?php
/**
 * Sam is an avid collector of numbers. Every time he finds a new number he throws it on the top of his number-pile. 
 * Help Sam organise his collection so he can take it to the International Number Collectors Conference in Cologne.
 * Given an array of numbers, your function should return an array of arrays, where each subarray contains all the duplicates of a particular number. 
 * Subarrays should be in the same order as the first occurence of the number they contain:
 * 
 * group([3, 2, 6, 2, 1, 3]) >>> [[3, 3], [2, 2], [6], [1]]
 * 
 * Assume the input is always going to be an array of numbers. If the input is an empty array, an empty array should be returned.
 */

 function group(array $numeros) {
    $resultado = [];

    //Mientras haya elementos en el array
    while (!empty($numeros)) {
        //Extraer el primer numero y crear el subarray
        $numeroActual = array_shift($numeros);
        $numerosAux = [$numeroActual];

        //Buscar duplicados e incluirlos en el subarray
        foreach ($numeros as $indice => $valor) {
            if ($numeroActual == $valor) {
                $numerosAux[] = $valor;
                unset($numeros[$indice]);
            }
        }

        //Añadri el subarray al array resultado.
        $resultado[] = $numerosAux;
    }

    return $resultado;
 }