<?php
$users = [];
$users2 = ['Jean'];
$users3 = ['Jean', 'P'];
$users4 = ['Jean', 'P', 'L'];
$users5 = ['Jean', 'P', 'L' , 'r'];
$users6 = ['Jean', 'P', 'L' , 'r' , 't'];
$users7 = ['Jean', 'P', 'L' , 'r' , 't' , 'y'];

function test($users)
{
    $totalUsers = count($users) ;
    $usersWide = count($users) - 1;
    switch (count($users)) {
        case 0:
            echo 'Soyez le 1er à liker';
            break;
        case 1:
            echo "$users[0] aime cette publication";
            break;
        case 2:
            echo "$users[0] et $users[1] aiment cette publication";
            break;

    }

    if ($totalUsers >= 3 && $totalUsers <=5){
       for($i=0;$i<$totalUsers-1;$i++){
           echo "$users[$i], ";
       }
        echo "et " . $users[$totalUsers - 1] . " aiment cette publication";


    } elseif ($totalUsers > 5) {
        echo "$users[0] et $usersWide autres personnes vous aiment";
    }
    echo '<br>';
}

test($users);
test($users2);
test($users3);
test($users4);
test($users5);
test($users6);
test($users7);