Transform a number representing the precision of another number, into a string containing the step value for HTML input number atttribute "step"

precision_to_step.php

<?php

// transforms p=3 into s=0.001
function precision_to_step($precision = 0)
{
  if ($precision <= 0) return '1';

  $step = str_pad('1', $precision, "0", STR_PAD_LEFT);
  $step = substr_replace($step, '0.', 0, 0);

  return $step;
}


foreach (range(-2, 5) as $precision)
{
  echo "p=$precision, s=". precision_to_step($precision). PHP_EOL;
}