<?php

$myString = "152258,152258,152258,152258,152261,152261,152261,152261,152261,152270,152270,152270,152287,152287,152287,152287";
$array = explode(",",$myString);
$unique = array_unique ( $array  );
$myUniqueString = implode(",",$unique);
echo $myUniqueString ;
?>

152258,152261,152270,152287