<?php

$ma_valeur = 1.23;
$mes_data = array(0.25,0.50,0.75,1.00,1.25,1.50,1.75,2.00,$ma_valeur);
sort($mes_data);

print_r(array_splice($mes_data, array_search($ma_valeur, $mes_data) - 2, 5));