Add minimal UUID v7 implementation

README.md

@@ -7,7 +7,7 @@ A small PHP class for generating [RFC 9562][RFC 9562] universally unique identif
 
 If all you want is a unique ID, you should call `uuid4()`.
 
-> Implementations SHOULD utilize UUID version 7 instead of UUID version 1 and 6 if possible.
+> Implementations SHOULD utilize UUIDv7 instead of UUIDv1 and UUIDv6 if possible.
 
 If you're regularly generating more than thousand UUIDs per second, you might want to use `uuid8()` instead of `uuid7()`. This implementation of `uuid8()` sacrifices some entropy compared to `uuid7()`, but offers 100 nanosecond granularity while being otherwise compatible.
 
@@ -27,6 +27,34 @@ function uuid4()
 echo uuid4();
 ```
 
+## Minimal UUID v7 implementation
+
+```php
+<?php
+function uuid7()
+{
+    static $last_timestamp = 0;
+    $unixts_ms = intval(microtime(true) * 1000);
+    if ($last_timestamp >= $unixts_ms) {
+        $unixts_ms = $last_timestamp + 1;
+    }
+    $last_timestamp = $unixts_ms;
+    $data = random_bytes(10);
+    $data[0] = chr((ord($data[0]) & 0x0f) | 0x70); // set version
+    $data[2] = chr((ord($data[2]) & 0x3f) | 0x80); // set variant
+    return vsprintf(
+        '%s%s-%s-%s-%s-%s%s%s',
+        str_split(
+            str_pad(dechex($unixts_ms), 12, '0', \STR_PAD_LEFT) .
+                bin2hex($data),
+            4
+        )
+    );
+}
+
+echo uuid7();
+```
+
 ## Installation
 
 If you need comparison tools or sortable identifiers like in versions 6, 7, and 8, you might find this small and fast package useful. It doesn't require any other dependencies.