opcache: Improve error message when OPcache is enabled dynamically

The error message will now advice on the `php_admin_value[opcache.enable]=1`
mistake. It will also send the message to OPcache’s logging facility instead of
the regular error handling logic during startup so that it will not be made
available to `error_get_last()`, since it is related to a specific request and
thus not actionable by a script either.

#19146 made a related change to `opcache.memory_consumption`.

Author: TimWolla

ext/opcache/zend_accelerator_module.c

@@ -167,7 +167,15 @@ static ZEND_INI_MH(OnEnable)
 				return SUCCESS;
 			}
 
-			zend_error(E_WARNING, ACCELERATOR_PRODUCT_NAME " can't be temporary enabled (it may be only disabled till the end of request)");
+			if (stage == ZEND_INI_STAGE_ACTIVATE) {
+				if (strcmp(sapi_module.name, "fpm-fcgi") == 0) {
+					zend_accel_error(ACCEL_LOG_WARNING, ACCELERATOR_PRODUCT_NAME " can't be temporary enabled. Are you using php_admin_value[opcache.enable]=1 in an individual pool's configuration?");
+				} else {
+					zend_accel_error(ACCEL_LOG_WARNING, ACCELERATOR_PRODUCT_NAME " can't be temporary enabled (it may be only disabled till the end of request)");
+				}
+			} else {
+				zend_error(E_WARNING, ACCELERATOR_PRODUCT_NAME " can't be temporary enabled (it may be only disabled till the end of request)");
+			}
 			return FAILURE;
 		} else {
 			*p = 0;

sapi/fpm/tests/opcache_enable_admin_value.phpt

@@ -0,0 +1,49 @@
+--TEST--
+Setting opcache.enable via php_admin_value fails gracefully
+--SKIPIF--
+<?php include "skipif.inc"; ?>
+--FILE--
+<?php
+
+require_once "tester.inc";
+
+$cfg = <<<EOT
+[global]
+error_log = {{FILE:LOG}}
+[unconfined]
+listen = {{ADDR}}
+pm = static
+pm.max_children = 1
+catch_workers_output = yes
+php_admin_value[opcache.enable] = On
+php_admin_flag[display_errors] = On
+php_admin_flag[display_startup_errors] = On
+php_admin_flag[log_errors] = On
+EOT;
+
+$code = <<<EOT
+<?php
+var_dump(error_get_last());
+EOT;
+
+$tester = new FPM\Tester($cfg, $code);
+$tester->start(iniEntries: [
+    'opcache.enable' => '0',
+    'opcache.log_verbosity_level' => '2',
+]);
+$tester->expectLogStartNotices();
+$tester->expectLogPattern("/Zend OPcache can't be temporary enabled. Are you using php_admin_value\\[opcache.enable\\]=1 in an individual pool's configuration?/");
+echo $tester
+    ->request()
+    ->getBody();
+$tester->terminate();
+$tester->close();
+
+?>
+--EXPECT--
+NULL
+--CLEAN--
+<?php
+require_once "tester.inc";
+FPM\Tester::clean();
+?>