A simple for
loop with some basic logic should suffice.
<?php
$a = [6,8,6,7,3,5,5,4,1,1,9,5,1,5,6];
$x = 0;
for($i=0;$i<=count($a);$i++) {
if(in_array($i, [5,9,12,14])) { //if we need a break point
$x++; //increment the break counter
echo PHP_EOL . str_repeat(' ', $x); //new line plus indentation
}
echo $a[$i] .' '; //echo the number and spacing
}