- array_map: documentation ( source)
- rsort: documentation ( source)
- array_unique: documentation ( source)
<?php
$array = array(13, -12, 8, 2, 5);
$final_array = array_unique(array_map('abs',$array)); // remove duplicates and apply abs() to all elements
rsort($final_array,SORT_NUMERIC); //reverse sort array numerically
echo $final_array[1]; //get second highest