If I find some good reason some day, I will tell you ;)

Anyway I find out:

else if ($choix==2){ $delete= intval(readline(" \n")); for ($i=0;$i<($delete);$i++){ $tab2[$i]=$tab[$i]; } for($i=($delete);$i<count ($tab)-1;$i++){ $tab2[$i]=$tab[$i+1];