Error: autoload_psr4.php not found Topic is solved

[SilverSurfer42]

I am having the exact same problem. I have followed the installation steps and am using this on a linux server that does not have cpanel or plesk. The autoload_psr4.php is located is this sub-directory here:
/libraries/vendor/composer/autoload_psr4.php

Zip file for installation is: Joomla_4.2.5-Stable-Full_Package.zip which was downloaded from downloads.joomla.org

Joomla! Instance :: Joomla! 4.2.5-Stable (Uaminifu) 8-November-2022
Joomla! Configured :: Not Found

Host Configuration :: OS: Linux | OS Version: 3.10.0-1160.6.1.el7.x86_64 | Technology: x86_64 | Web Server: Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/8.1.13 | Encoding: gzip, deflate, br | System TMP Writable: Yes | Free Disk Space : 1741.74 GiB |

PHP Configuration :: Version: 8.1.13 | PHP API: apache2handler | Session Path Writable: Yes | Display Errors: 0 | Error Reporting: 22527 | Log Errors To: | Last Known Error: | Register Globals: | Magic Quotes: | Safe Mode: | Allow url fopen: 1 | Open Base: | Uploads: 1 | Max. Upload Size: 30M | Max. POST Size: 30M | Max. Input Time: 60 | Max. Execution Time: 30 | Memory Limit: 256M

Database Configuration :: Database Credentials incomplete or not available Nothing to display.
Missing credentials detected: Connection Type missing | Database Name missing |MySQL Host missing | Table Prefix missing | Database Username missing | Database Password missing |User Privileges : Unknown

PHP Extensions :: Core (8.1.13) | date (8.1.13) | libxml (8.1.13) | openssl (8.1.13) | pcre (8.1.13) | zlib (8.1.13) | filter (8.1.13) | hash (8.1.13) | json (8.1.13) | Reflection (8.1.13) | SPL (8.1.13) | session (8.1.13) | standard (8.1.13) | apache2handler (8.1.13) | bcmath (8.1.13) | bz2 (8.1.13) | calendar (8.1.13) | ctype (8.1.13) | curl (8.1.13) | dom (20031129) | mbstring (8.1.13) | fileinfo (8.1.13) | ftp (8.1.13) | gd (8.1.13) | gettext (8.1.13) | iconv (8.1.13) | exif (8.1.13) | mysqlnd (mysqlnd 8.1.13) | PDO (8.1.13) | Phar (8.1.13) | posix (8.1.13) | shmop (8.1.13) | SimpleXML (8.1.13) | sockets (8.1.13) | sodium (8.1.13) | sqlite3 (8.1.13) | sysvmsg (8.1.13) | sysvsem (8.1.13) | sysvshm (8.1.13) | tokenizer (8.1.13) | xml (8.1.13) | xmlwriter (8.1.13) | xsl (8.1.13) | mcrypt (1.0.5) | mysqli (8.1.13) | pdo_mysql (8.1.13) | pdo_sqlite (8.1.13) | xmlreader (8.1.13) | zip (1.21.1) | Zend Engine (4.1.13) |
Potential Missing Extensions ::

Switch User Environment :: PHP CGI: No | Server SU: No | PHP SU: No | Potential Ownership Issues: Yes

Apache Modules :: core | mod_so | http_core | mod_access_compat | mod_actions | mod_alias | mod_allowmethods | mod_auth_basic | mod_auth_digest | mod_authn_anon | mod_authn_core | mod_authn_dbd | mod_authn_dbm | mod_authn_file | mod_authn_socache | mod_authz_core | mod_authz_dbd | mod_authz_dbm | mod_authz_groupfile | mod_authz_host | mod_authz_owner | mod_authz_user | mod_autoindex | mod_cache | mod_cache_disk | mod_data | mod_dbd | mod_deflate | mod_dir | mod_dumpio | mod_echo | mod_env | mod_expires | mod_ext_filter | mod_filter | mod_headers | mod_include | mod_info | mod_log_config | mod_logio | mod_mime_magic | mod_mime | mod_negotiation | mod_remoteip | mod_reqtimeout | mod_rewrite | mod_setenvif | mod_slotmem_plain | mod_slotmem_shm | mod_socache_dbm | mod_socache_memcache | mod_socache_shmcb | mod_status | mod_substitute | mod_suexec | mod_unique_id | mod_unixd | mod_userdir | mod_version | mod_vhost_alias | mod_dav | mod_dav_fs | mod_dav_lock | mod_lua | prefork | mod_proxy | mod_lbmethod_bybusyness | mod_lbmethod_byrequests | mod_lbmethod_bytraffic | mod_lbmethod_heartbeat | mod_proxy_ajp | mod_proxy_balancer | mod_proxy_connect | mod_proxy_express | mod_proxy_fcgi | mod_proxy_fdpass | mod_proxy_ftp | mod_proxy_http | mod_proxy_scgi | mod_proxy_wstunnel | mod_ssl | mod_systemd | mod_cgi | mod_php | Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/8.1.13 |
Potential Missing Modules ::

Core Folders :: images/ (755) | components/ (755) | modules/ (755) | plugins/ (755) | language/ (755) | templates/ (755) | cache/ (755) | logs/ (---) | tmp/ (755) | administrator/components/ (755) | administrator/modules/ (755) | administrator/language/ (755) | administrator/templates/ (755) | administrator/logs/ (755) |

Elevated Permissions (First 10) ::

Components :: Site ::
Core ::
3rd Party::

Components :: Admin ::
Core :: com_categories (4.0.0) ? | com_admin (4.0.0) ? | com_installer (4.0.0) ? | com_users (4.0.0) ? | com_media (3.0.0) ? | com_workflow (4.0.0) ? | com_ajax (4.0.0) ? | com_cache (4.0.0) ? | com_scheduler (4.1.0) ? | com_newsfeeds (4.0.0) ? | com_mails (4.0.0) ? | com_plugins (4.0.0) ? | com_banners (4.0.0) ? | com_tags (4.0.0) ? | com_finder (4.0.0) ? | com_languages (4.0.0) ? | com_checkin (4.0.0) ? | com_config (4.0.0) ? | com_privacy (3.9.0) ? | com_redirect (4.0.0) ? | com_cpanel (4.0.0) ? | com_joomlaupdate (4.0.3) ? | com_templates (4.0.0) ? | com_menus (4.0.0) ? | com_associations (4.0.0) ? | com_login (4.0.0) ? | com_postinstall (4.0.0) ? | com_fields (4.0.0) ? | com_wrapper (4.0.0) ? | com_contenthistory (4.0.0) ? | com_messages (4.0.0) ? | com_modules (4.0.0) ? | com_actionlogs (3.9.0) ? | com_content (4.0.0) ? |
3rd Party::

Modules :: Site ::
Core :: mod_feed (3.0.0) ? | mod_articles_categories (3.0.0) ? | mod_articles_category (3.0.0) ? | mod_footer (3.0.0) ? | mod_users_latest (3.0.0) ? | mod_languages (3.5.0) ? | mod_whosonline (3.0.0) ? | mod_syndicate (3.0.0) ? | mod_wrapper (3.0.0) ? | mod_banners (3.0.0) ? | mod_login (3.0.0) ? | mod_breadcrumbs (3.0.0) ? | mod_stats (3.0.0) ? | mod_tags_similar (3.1.0) ? | mod_articles_popular (3.0.0) ? | mod_articles_latest (3.0.0) ? | mod_finder (3.0.0) ? | mod_related_items (3.0.0) ? | mod_random_image (3.0.0) ? | mod_tags_popular (3.1.0) ? | mod_articles_archive (3.0.0) ? | mod_menu (3.0.0) ? | mod_custom (3.0.0) ? | mod_articles_news (3.0.0) ? |
3rd Party::

Modules :: Admin ::
Core :: mod_feed (3.0.0) ? | mod_multilangstatus (3.0.0) ? | mod_loginsupport (4.0.0) ? | mod_messages (4.0.0) ? | mod_version (3.0.0) ? | mod_submenu (3.0.0) ? | mod_latest (3.0.0) ? | mod_sampledata (3.8.0) ? | mod_logged (3.0.0) ? | mod_popular (3.0.0) ? | mod_toolbar (3.0.0) ? | mod_login (3.0.0) ? | mod_quickicon (3.0.0) ? | mod_post_installation_messages (4.0.0) ? | mod_stats_admin (3.0.0) ? | mod_latestactions (3.9.0) ? | mod_privacy_status (4.0.0) ? | mod_title (3.0.0) ? | mod_privacy_dashboard (3.9.0) ? | mod_frontend (4.0.0) ? | mod_menu (3.0.0) ? | mod_custom (3.0.0) ? | mod_user (4.0.0) ? |
3rd Party::

Libraries ::
Core ::
3rd Party::

Plugins ::
Core :: plg_api-authentication_basic (4.0.0) ? | plg_api-authentication_token (4.0.0) ? | plg_multifactorauth_fixed (4.2.0) ? | plg_multifactorauth_yubikey (3.2.0) ? | plg_multifactorauth_email (4.2.0) ? | plg_multifactorauth_totp (3.2.0) ? | plg_multifactorauth_webauthn (4.2.0) ? | plg_editors-xtd_readmore (3.0.0) ? | plg_editors-xtd_pagebreak (3.0.0) ? | plg_editors-xtd_image (3.0.0) ? | plg_editors-xtd_fields (3.7.0) ? | plg_editors-xtd_module (3.5.0) ? | plg_editors-xtd_menu (3.7.0) ? | plg_editors-xtd_article (3.0.0) ? | plg_extension_joomla (3.0.0) ? | plg_extension_finder (4.0.0) ? | plg_extension_namespacemap (4.0.0) ? | plg_behaviour_versionable (4.0.0) ? | plg_behaviour_taggable (4.0.0) ? | plg_task_check_files (4.1) ? | plg_task_site_status (4.1) ? | plg_task_demo_tasks (4.1) ? | plg_task_requests (4.1) ? | plg_finder_tags (3.0.0) ? | plg_finder_content (3.0.0) ? | plg_finder_categories (3.0.0) ? | plg_finder_contacts (3.0.0) ? | plg_finder_newsfeeds (3.0.0) ? | plg_content_joomla (3.0.0) ? | plg_content_emailcloak (3.0.0) ? | plg_content_pagebreak (3.0.0) ? | plg_content_finder (3.0.0) ? | plg_content_confirmconsent (3.9.0) ? | plg_content_fields (3.7.0) ? | plg_content_loadmodule (3.0.0) ? | plg_content_pagenavigation (3.0.0) ? | plg_content_vote (3.0.0) ? | plg_captcha_recaptcha (3.4.0) ? | plg_captcha_recaptcha_invisible (3.8) ? | plg_fields_media (3.7.0) ? | plg_fields_editor (3.7.0) ? | plg_fields_text (3.7.0) ? | plg_fields_radio (3.7.0) ? | plg_fields_imagelist (3.7.0) ? | plg_fields_usergrouplist (3.7.0) ? | plg_fields_textarea (3.7.0) ? | plg_fields_user (3.7.0) ? | plg_fields_subform (4.0.0) ? | plg_fields_color (3.7.0) ? | plg_fields_sql (3.7.0) ? | plg_fields_list (3.7.0) ? | plg_fields_calendar (3.7.0) ? | plg_fields_integer (3.7.0) ? | plg_fields_url (3.7.0) ? | plg_fields_checkboxes (3.7.0) ? | plg_user_joomla (3.0.0) ? | plg_user_terms (3.9.0) ? | plg_user_contactcreator (3.0.0) ? | plg_user_profile (3.0.0) ? | plg_user_token (3.9.0) ? | plg_installer_override (4.0.0) ? | plg_installer_urlinstaller (3.6.0) ? | plg_installer_webinstaller (4.0.0) ? | plg_installer_packageinstaller (3.6.0) ? | plg_installer_folderinstaller (3.6.0) ? | plg_webservices_media (4.1.0) ? | plg_webservices_tags (4.0.0) ? | plg_webservices_plugins (4.0.0) ? | plg_webservices_content (4.0.0) ? | plg_webservices_menus (4.0.0) ? | plg_webservices_banners (4.0.0) ? | plg_webservices_messages (4.0.0) ? | plg_webservices_installer (4.0.0) ? | plg_webservices_privacy (4.0.0) ? | plg_webservices_users (4.0.0) ? | plg_webservices_languages (4.0.0) ? | plg_webservices_modules (4.0.0) ? | plg_webservices_templates (4.0.0) ? | plg_webservices_redirect (4.0.0) ? | plg_webservices_newsfeeds (4.0.0) ? | plg_webservices_config (4.0.0) ? | plg_privacy_actionlogs (3.9.0) ? | plg_privacy_content (3.9.0) ? | plg_privacy_user (3.9.0) ? | plg_privacy_consents (3.9.0) ? | plg_privacy_message (3.9.0) ? | plg_media-action_rotate (4.0.0) ? | plg_media-action_crop (4.0.0) ? | plg_media-action_resize (4.0.0) ? | plg_actionlog_joomla (3.9.0) ? | plg_workflow_notification (4.0.0) ? | plg_workflow_featuring (4.0.0) ? | plg_workflow_publishing (4.0.0) ? | plg_authentication_joomla (3.0.0) ? | plg_authentication_ldap (3.0.0) ? | plg_authentication_cookie (3.0.0) ? | plg_filesystem_local (4.0.0) ? | plg_quickicon_extensionupdate (3.0.0) ? | plg_quickicon_phpversioncheck (3.7.0) ? | plg_quickicon_downloadkey (4.0.0) ? | plg_quickicon_joomlaupdate (3.0.0) ? | plg_quickicon_overridecheck (4.0.0) ? | plg_quickicon_privacycheck (3.9.0) ? | plg_sampledata_multilang (4.0.0) ? | plg_system_languagefilter (3.0.0) ? | plg_system_actionlogs (3.9.0) ? | plg_system_httpheaders (4.0.0) ? | plg_system_skipto (4.0.0) ? | plg_system_stats (3.5.0) ? | plg_system_jooa11y (4.2.0) ? | plg_system_privacyconsent (3.9.0) ? | plg_system_accessibility (4.0.0) ? | plg_system_sef (3.0.0) ? | plg_system_languagecode (3.0.0) ? | plg_system_shortcut (4.2.0) ? | plg_system_fields (3.7.0) ? | plg_system_debug (3.0.0) ? | plg_system_schedulerunner (4.1) ? | plg_system_remember (3.0.0) ? | plg_system_log (3.0.0) ? | plg_system_logrotation (3.9.0) ? | plg_system_updatenotification (3.5.0) ? | plg_system_cache (3.0.0) ? | plg_system_logout (3.0.0) ? | plg_system_task_notification (4.1) ? | plg_system_sessiongc (3.8.6) ? | plg_system_redirect (3.0.0) ? | plg_system_webauthn (4.0.0) ? | plg_system_highlight (3.0.0) ? |
3rd Party:: plg_editors_tinymce (5.10.5) ? | plg_editors_codemirror (5.65.6) ? |

Templates :: Site :: cassiopeia (1.0) ? |
Templates :: Admin :: atum (1.0) ? |

[Webdongle]

PHP API: apache2handler might be a problem ... search your Host's help for f/cgi or ask your Host.

[SilverSurfer42]

Are you saying that I need to switch to fastcgi from apache2handler? Or there something wrong with the apache2handler?

Here is the phpinfo()

Server API Apache 2.0 Handler

apache2handler
Apache Version Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/8.1.13
Apache API Version 20120211
Server Administrator [email protected]
Hostname:Port domain_name:0
User/Group apache(48)/48
Max Requests Per Child: 0 - Keep Alive: on - Max Per Connection: 100
Timeouts Connection: 60 - Keep-Alive: 5
Virtual Server Yes
Server Root /etc/httpd
Loaded Modules core mod_so http_core mod_access_compat mod_actions mod_alias mod_allowmethods mod_auth_basic mod_auth_digest mod_authn_anon mod_authn_core mod_authn_dbd mod_authn_dbm mod_authn_file mod_authn_socache mod_authz_core mod_authz_dbd mod_authz_dbm mod_authz_groupfile mod_authz_host mod_authz_owner mod_authz_user mod_autoindex mod_cache mod_cache_disk mod_data mod_dbd mod_deflate mod_dir mod_dumpio mod_echo mod_env mod_expires mod_ext_filter mod_filter mod_headers mod_include mod_info mod_log_config mod_logio mod_mime_magic mod_mime mod_negotiation mod_remoteip mod_reqtimeout mod_rewrite mod_setenvif mod_slotmem_plain mod_slotmem_shm mod_socache_dbm mod_socache_memcache mod_socache_shmcb mod_status mod_substitute mod_suexec mod_unique_id mod_unixd mod_userdir mod_version mod_vhost_alias mod_dav mod_dav_fs mod_dav_lock mod_lua prefork mod_proxy mod_lbmethod_bybusyness mod_lbmethod_byrequests mod_lbmethod_bytraffic mod_lbmethod_heartbeat mod_proxy_ajp mod_proxy_balancer mod_proxy_connect mod_proxy_express mod_proxy_fcgi mod_proxy_fdpass mod_proxy_ftp mod_proxy_http mod_proxy_scgi mod_proxy_wstunnel mod_ssl mod_systemd mod_cgi mod_php

[Webdongle]

Are you saying that I need to switch to fastcgi from apache2handler? ...

Yes

[ceford]

The problem seems to be the database - it is not connected, so the configuration.php and autoload_psr.php files were never created on installation. You must have a database and a database user ready before installing Joomla. Have you opened your database with phpMyAdmin to see if there are any tables.

On the PHP handler, see this article:

https://docs.joomla.org/J4.x:Apache_PHP_Handler

[Webdongle]

Yes Ownership issues. Search your Host's help for f/cgi or ask your Host

[SilverSurfer42]

Well, I finally figured this out after wasting a lot of time trying to get FastCGI working on the server (Centos 7). Joomla 4 installed just fine once I had the correct permissions for the website document root. You can leave the API handler set to apache2handler. Basically, if the web group for the apache server is apache the change the owner and group for the directory to apache.
i.e. chown -R apache:apache /var/www/html/joomla-directory. Then make that directory writeable so the install program can make and save the appropriate files.
i.e. g+w /var/www/html/joomla-directory
Then just let Joomla install itself.