Search notes:

include/generated/autoconf.h

include/generated/autoconf.h contains a list of CONFIG_* macro definitions: 
/*
 * Automatically generated file; DO NOT EDIT.
 * Linux/x86 6.5.0-rc7 Kernel Configuration
 */
#define CONFIG_RING_BUFFER 1
#define CONFIG_HAVE_ARCH_SECCOMP_FILTER 1
#define CONFIG_SND_PROC_FS 1
#define CONFIG_SCSI_DMA 1
…
This file is updated by make syncconfig when .config (or the file referred to by KCONFIG_CONFIG) changes.
kernel/gen_kheaders.sh says this about autoconf.h:
When Kconfig regenerates include/generated/autoconf.h, its timestamp is updated, but the contents might be still the same. When any CONFIG option is changed, Kconfig touches the corresponding timestamp file include/config/*. Hence, the md5sum detects the configuration change anyway. We do not need to check include/generated/autoconf.h explicitly.

See also

generated/autoconf.h is prominently included from include/linux/kconfig.h.
include/config/auto.conf
include/generated/
The default value of KCONFIG_AUTOHEADER is include/generated/autoconf.h

Index

Fatal error: Uncaught PDOException: SQLSTATE[HY000]: General error: 8 attempt to write a readonly database in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php:78 Stack trace: #0 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(78): PDOStatement->execute(Array) #1 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(30): insert_webrequest_('/notes/Linux/ke...', 1759391081, '216.73.216.42', 'Mozilla/5.0 App...', NULL) #2 /home/httpd/vhosts/renenyffenegger.ch/httpsdocs/notes/Linux/kernel/source/include/generated/autoconf_h(60): insert_webrequest() #3 {main} thrown in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php on line 78