The manual regarding preloading seems to be off regarding when to use opcache_compile_file vs require:

Quoting https://www.php.net/manual/en/opcache.preloading.php -- emphasis mine:

opcache_compile_file() can load files in any order. That is, if a.php defines class A and b.php defines class B that extends A, then opcache_compile_file() can load those two files in any order. When using include, however, a.php must be included first.

Which approach is better therefore depends on the desired behavior. With code that would otherwise use an autoloader, opcache_compile_file() allows for greater flexibility. With code that would otherwise be loaded manually, include will be more robust.

---

The result of the following simple test indicate the contrary, though.

Running

require=0 php -d opcache.enable_cli=1 -d opcache.preload=t/preload.php t/index.php >t/compile.txt

and

require=1 php -d opcache.enable_cli=1 -d opcache.preload=t/preload.php t/index.php >t/require.txt

results in the following (stripped down) differences:

--- t/compile.txt
+++ t/require.txt
@@ -1,13 +1,15 @@
-array(1) {
+autoload(b) -> require b.php
+autoload(c) -> require c.php
+array(4) {
   [0]=>
   string(45) "/Users/mike/Sources/php-preload/t/preload.php"
+  [1]=>
+  string(39) "/Users/mike/Sources/php-preload/t/a.php"
+  [2]=>
+  string(39) "/Users/mike/Sources/php-preload/t/b.php"
+  [3]=>
+  string(39) "/Users/mike/Sources/php-preload/t/c.php"
 }
-
-Warning: Can't preload class c with unresolved initializer for static property $c in /Users/mike/Sources/php-preload/t/c.php on line 3
-
-Warning: Can't preload unlinked class b: Parent with unresolved initializers c in /Users/mike/Sources/php-preload/t/b.php on line 3
-
-Warning: Can't preload unlinked class a: Unknown parent b in /Users/mike/Sources/php-preload/t/a.php on line 3
 Array
 (
     [opcache_enabled] => 1
@@ -49,13 +51,20 @@
 
     [preload_statistics] => Array
         (
             [functions] => Array
                 (
                     [0] => {closure}
                     [1] => {closure}
                 )
 
+            [classes] => Array
+                (
+                    [0] => c
+                    [1] => b
+                    [2] => a
+                )
+
             [scripts] => Array
                 (
                     [0] => /Users/mike/Sources/php-preload/t/preload.php

Judge for yourself, but it looks like using require plus autoload is more robust.