<?php
        $array = [
        	['nome' => 'Luis', 'id' => 1], 
        	['nome' => 'Rui', 'id' => 2],
        	['nome' => 'Joao', 'id' => 3],
        	['nome' => 'Joaquim', 'id' => 4],
        	['nome' => 'Jorge', 'id' => 5],
        ];
    	
    	$iterator = new RecursiveIteratorIterator(new RecursiveArrayIterator($array));
    
    	$nomes = [];
    	
    	foreach ($iterator as $key => $value)
            if ($key == 'nome') $nomes[] = $value;
       
        
        var_dump($nomes);