--- /dev/null
+<?php
+/**
+ * Random_* Compatibility Library
+ * for using the new PHP 7 random_* API in PHP 5 projects
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015 Paragon Initiative Enterprises
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+/**
+ * Fetch a random integer between $min and $max inclusive
+ *
+ * @param int $min
+ * @param int $max
+ *
+ * @throws Exception
+ *
+ * @return int
+ */
+function random_int($min, $max)
+{
+ /**
+ * Type and input logic checks
+ *
+ * If you pass it a float in the range (~PHP_INT_MAX, PHP_INT_MAX)
+ * (non-inclusive), it will sanely cast it to an int. If you it's equal to
+ * ~PHP_INT_MAX or PHP_INT_MAX, we let it fail as not an integer. Floats
+ * lose precision, so the <= and => operators might accidentally let a float
+ * through.
+ */
+
+ try {
+ $min = RandomCompat_intval($min);
+ } catch (TypeError $ex) {
+ throw new TypeError(
+ 'random_int(): $min must be an integer'
+ );
+ }
+ try {
+ $max = RandomCompat_intval($max);
+ } catch (TypeError $ex) {
+ throw new TypeError(
+ 'random_int(): $max must be an integer'
+ );
+ }
+
+ /**
+ * Now that we've verified our weak typing system has given us an integer,
+ * let's validate the logic then we can move forward with generating random
+ * integers along a given range.
+ */
+ if ($min > $max) {
+ throw new Error(
+ 'Minimum value must be less than or equal to the maximum value'
+ );
+ }
+ if ($max === $min) {
+ return $min;
+ }
+
+ /**
+ * Initialize variables to 0
+ *
+ * We want to store:
+ * $bytes => the number of random bytes we need
+ * $mask => an integer bitmask (for use with the &) operator
+ * so we can minimize the number of discards
+ */
+ $attempts = $bits = $bytes = $mask = $valueShift = 0;
+
+ /**
+ * At this point, $range is a positive number greater than 0. It might
+ * overflow, however, if $max - $min > PHP_INT_MAX. PHP will cast it to
+ * a float and we will lose some precision.
+ */
+ $range = $max - $min;
+
+ /**
+ * Test for integer overflow:
+ */
+ if (!is_int($range)) {
+ /**
+ * Still safely calculate wider ranges.
+ * Provided by @CodesInChaos, @oittaa
+ *
+ * @ref https://gist.github.com/CodesInChaos/03f9ea0b58e8b2b8d435
+ *
+ * We use ~0 as a mask in this case because it generates all 1s
+ *
+ * @ref https://eval.in/400356 (32-bit)
+ * @ref http://3v4l.org/XX9r5 (64-bit)
+ */
+ $bytes = PHP_INT_SIZE;
+ $mask = ~0;
+ } else {
+ /**
+ * $bits is effectively ceil(log($range, 2)) without dealing with
+ * type juggling
+ */
+ while ($range > 0) {
+ if ($bits % 8 === 0) {
+ ++$bytes;
+ }
+ ++$bits;
+ $range >>= 1;
+ $mask = $mask << 1 | 1;
+ }
+ $valueShift = $min;
+ }
+
+ /**
+ * Now that we have our parameters set up, let's begin generating
+ * random integers until one falls between $min and $max
+ */
+ do {
+ /**
+ * The rejection probability is at most 0.5, so this corresponds
+ * to a failure probability of 2^-128 for a working RNG
+ */
+ if ($attempts > 128) {
+ throw new Exception(
+ 'random_int: RNG is broken - too many rejections'
+ );
+ }
+
+ /**
+ * Let's grab the necessary number of random bytes
+ */
+ $randomByteString = random_bytes($bytes);
+ if ($randomByteString === false) {
+ throw new Exception(
+ 'Random number generator failure'
+ );
+ }
+
+ /**
+ * Let's turn $randomByteString into an integer
+ *
+ * This uses bitwise operators (<< and |) to build an integer
+ * out of the values extracted from ord()
+ *
+ * Example: [9F] | [6D] | [32] | [0C] =>
+ * 159 + 27904 + 3276800 + 201326592 =>
+ * 204631455
+ */
+ $val = 0;
+ for ($i = 0; $i < $bytes; ++$i) {
+ $val |= ord($randomByteString[$i]) << ($i * 8);
+ }
+
+ /**
+ * Apply mask
+ */
+ $val &= $mask;
+ $val += $valueShift;
+
+ ++$attempts;
+ /**
+ * If $val overflows to a floating point number,
+ * ... or is larger than $max,
+ * ... or smaller than $min,
+ * then try again.
+ */
+ } while (!is_int($val) || $val > $max || $val < $min);
+ return (int) $val;
+}
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