gistfile1.php

<?php

var_dump( array_combine(range(1,12), array_map(function($i) { return date('M', mktime(1,0,0,$i,1,1970)); }, range(1,12))) );
/**
array(12) {
  [1] =>
  string(3) "Jan"
  [2] =>
  string(3) "Feb"
  [3] =>
  string(3) "Mar"
  [4] =>
  string(3) "Apr"
  [5] =>
  string(3) "May"
  [6] =>
  string(3) "Jun"
  [7] =>
  string(3) "Jul"
  [8] =>
  string(3) "Aug"
  [9] =>
  string(3) "Sep"
  [10] =>
  string(3) "Oct"
  [11] =>
  string(3) "Nov"
  [12] =>
  string(3) "Dec"
}
*/