Add polyfill for spl_object_id

composer.json

@@ -32,7 +32,8 @@
             "Psalm\\": "src/Psalm"
         },
         "files": [
-            "src/functions.php"
+            "src/functions.php",
+            "src/spl_object_id.php"
         ]
     },
     "autoload-dev": {

src/spl_object_id.php

@@ -0,0 +1,52 @@
+<?php declare(strict_types=1);
+
+/**
+ * PHP Polyfill for spl_object_id() for PHP <= 7.1
+ * This file will be included even in releases which will analyze PHP 7.2,
+ * there aren't any major compatibilities preventing analysis of PHP 7.2 from running in PHP 7.1.
+ */
+if (!function_exists('spl_object_id')) {
+    if (function_exists('runkit_object_id') &&
+        !(new ReflectionFunction('runkit_object_id'))->isUserDefined()) {
+        /**
+         * See https://github.com/runkit7/runkit_object_id for a faster native version for php <= 7.1
+         *
+         * @param object $object
+         * @return int The object id
+         */
+        function spl_object_id($object) : int
+        {
+            return runkit_object_id($object);
+        }
+    } elseif (PHP_INT_SIZE === 8) {
+        /**
+         * See https://github.com/runkit7/runkit_object_id for a faster native version for php <= 7.1
+         *
+         * @param object $object
+         * @return int (The object id, XORed with a random number)
+         */
+        function spl_object_id($object) : int
+        {
+            $hash = spl_object_hash($object);
+            // Fit this into a php long (32-bit or 64-bit signed int).
+            // The first 16 hex digits (64 bytes) vary, the last 16 don't.
+            // Values are usually padded with 0s at the front.
+            return intval(substr($hash, 1, 15), 16);
+        }
+    } else {
+        /**
+         * See https://github.com/runkit7/runkit_object_id for a faster native version for php <= 7.1
+         *
+         * @param object $object
+         * @return int (The object id, XORed with a random number)
+         */
+        function spl_object_id($object) : int
+        {
+            $hash = spl_object_hash($object);
+            // Fit this into a php long (32-bit or 64-bit signed int).
+            // The first 16 hex digits (64 bytes) vary, the last 16 don't.
+            // Values are usually padded with 0s at the front.
+            return intval(substr($hash, 9, 7), 16);
+        }
+    }
+}