Deterministically generates an unpredictable number from the input within a given range

determine.php

<?php

/**
 * Deterministically generates an unpredictable number from the input within a given range
 * Intended for int|float but will accept anything
 * 
 * Uses MD5 to generate a number between 0–268435455 then "scales" that number into the desired range
 *
 * @param mixed     $input     Variable to use as seed
 * @param int|float $min       Lower range for desired output
 * @param int|float $max       Upper range for desired output
 * @param int       $precision Optional number of decimal digits to round to
 *
 * @return int|float Number determined by $input
 */
function determine($input, $min, $max, $precision = false) {

	// Ensure input is usable
	if (!is_string($input)) $input = serialize($input);

	// Generate seed - hexdec expects 8-bit signed hexadecimal integer
	// and it's easier to work with positive ints, so only use first 7 chars
	$hash   = md5($input);
	$seed   = hexdec(substr($hash, 0, 7));

	// Determine result within desired range
	$range  = $max - $min;
	$ratio  = 268435455 / $range;
	$output = $seed / $ratio + $min;

	// Round?
	if ($precision !== false && $precision >= 0)
		$output = round($output, $precision);

	// If number has no decimals, convert to int
	if (intval($output) == $output)
		$output = intval($output);

	return $output;

}