stamhe · June 25, 2017 14:20 · Nov 17, 2015
diff --git a/SnowFlake.php b/SnowFlake.php
@@ -0,0 +1,102 @@
+<?php
+
+/**
+ * SnowFlake ID Generator
+ * Based on Twitter Snowflake to generate unique ID across multiple
+ * datacenters and databases without having duplicates.
+ * 
+ * 
+ * SnowFlake Layout
+ *
+ * 1 sign bit -- 0 is positive, 1 is negative
+ * 41 bits -- milliseconds since epoch
+ * 5 bits -- datacenter ID
+ * 5 bits -- machine ID
+ * 12 bits -- sequence number
+ * 
+ * Total 64 bit integer/string
+ */
+
+class SnowFlake {
+    /**
+     * Offset from Unix Epoch
+     * Unix Epoch : January 1 1970 00:00:00 GMT
+     * Epoch Offset : January 1 2000 00:00:00 GMT
+     */
+    CONST EPOCH_OFFSET = 9466848000000;
+
+    /**
+     * @var mixed
+     */
+    private $datacenter_id;
+
+    /**
+     * @var mixed
+     */
+    private $machine_id;
+
+    /**
+     * @var null|int
+     */
+    private $lastTime = null;
+
+    /**
+     * @var int
+     */
+    private $sequence  = 1;
+
+    /**
+     * Constructor to set required paremeters
+     * 
+     * @param mixed $datacenter_id    Unique ID for datacenter (if multiple locations are used)
+     * @param mixed $machine_id       Unique ID for machine (if multiple machines are used)
+     */
+    public function __construct($datacenter_id, $machine_id)
+    {
+        $this->datacenter_id = $datacenter_id;
+        $this->machine_id = $machine_id;
+    }
+
+    /**
+     * Generate an unique ID based on SnowFlake
+     * 
+     * @return string  Unique ID
+     */
+    public function generateID() {
+        $sign = 0; // default 0
+
+        $time = (int)($this->getUnixTimestamp() - self::EPOCH_OFFSET);
+
+        $sequence = $this->getNextSequence($time);
+
+        $this->lastTime = $time;
+
+        $id = ($sign << 1) | ($time << 41) | ($this->datacenter_id << 5) | ($this->machine_id << 5) | ($sequence << 12) ;
+        return (string)$id;
+    }
+
+    /**
+     * Get UNIX timestamp in microseconds
+     * 
+     * @return int  Timestamp in microseconds
+     */
+    private function getUnixTimestamp()
+    {
+        return floor(microtime(true) * 1000);
+    }
+
+    /**
+     * Get the next sequence number if $time
+     * was already used
+     * 
+     * @param  int $time    (micro)timestamp from EPOCH_OFFSET
+     * @return int          Sequence number
+     */
+    private function getNextSequence($time)
+    {
+        if($time === $this->lastTime) {
+            return ++$this->sequence;
+        }
+        return $this->sequence;
+    }
+}