- number_format: documentation ( source)
<?php
$my_num = 131510;
$dec = number_format($my_num / 100, 3, '.', ',');
echo $dec . "\n";
echo (float) $dec/100;
echo PHP_EOL;
$foo = "10510";
echo (float) number_format((float)$foo / 100, 2, '.', ''); // Outputs -> 105.00