<?php

function array_percentage($array, $percentage) 
{
    shuffle($array);
    $count = count($array);
    $result = array_slice($array, 0, ceil($count*$percentage/100));
    return $result;
}


$names = "foo\nbar\nbaz\nbaq\nlaz\nlaz\nlaz";
$namesArray = explode("\n", $names);

print_r(array_percentage($namesArray, 5));

Array
(
    [0] => laz
)