Unable to access Plesk panel on a Windows Server: Failed opening required 'auth.php' (include_path='.;C:\php\pear') in Unknown on line 0

Gabriel Aznarez

Updated December 10, 2025 12:12

Plesk for Windows kb: technical

Applicable to:

Plesk Obsidian for Windows

Symptoms

Plesk is not accessible with the following message:

Unknown: failed to open stream: No such file or directory in Unknown on line 0

Fatal error: Unknown: Failed opening required 'auth.php' (include_path='.;C:\php\pear') in Unknown on line 0
In some cases the Plesk Panel may load but an attempt to navigate to a given section fails with:

SyntaxError: Unexpected token '<', "<br /<b>"... is not valid JSON
The file %plesk_dir%admin\conf\php.ini is empty or incomplete containing only a few directives.

Cause

The php.ini Plesk configuration file does not contain all the required directives.

Resolution

Connect to the server via RDP.
Navigate to the directory %plesk_dir%admin\conf\
Add the following content inside the file php.ini:

Full php.ini file content

[PHP]
extension_dir="C:\Program Files (x86)\Plesk\admin\engine"
max_execution_time=7200
log_errors=On
display_errors=Off
error_reporting=E_ALL & ~E_NOTICE & ~E_STRICT & ~E_DEPRECATED
error_log="C:\Program Files (x86)\Plesk\admin\logs\php_error.log"
register_globals=Off
post_max_size=2147483647
include_path="C:\Program Files (x86)\Plesk\admin\plib"
fastcgi.impersonate=0
sys_temp_dir="C:\Program Files (x86)\Plesk\PrivateTemp"
upload_tmp_dir="C:\Program Files (x86)\Plesk\PrivateTemp"
upload_max_filesize=2147483647
max_file_uploads=99999
max_input_vars=2000
cgi.force_redirect= 0
curl.cainfo="C:\Program Files (x86)\Plesk\admin\conf\cacert.pem"
openssl.cafile="C:\Program Files (x86)\Plesk\admin\conf\cacert.pem"
memory_limit=256M
swkey.product_name="plesk-win"
swkey.repository_dir="C:\Program Files (x86)\Plesk\admin\repository"
expose_php=Off
magic_quotes_gpc=Off
magic_quotes_runtime=Off
[Session]
session.save_path="C:\Program Files (x86)\Plesk\admin\sessions"
[opcache]
zend_extension=opcache
opcache.enable=1
opcache.memory_consumption=24
opcache.error_log="C:\Program Files (x86)\Plesk\admin\logs\php_opcache.log"
[php_curl]
extension=curl
[php_imap]
extension=imap
[php_openssl]
extension=openssl
[php_sodium]
extension=sodium
[php_xsl]
extension=xsl
[php_lock_manager]
extension=lock_manager
[php_plesk_util]
extension=plesk_util
[php_psakey]
extension=psakey
[php_gd2]
extension=gd2
[php_intl]
extension=intl
[php_aps_php]
extension=aps_php
[php_fileinfo]
extension=fileinfo
[php_ftp]
extension=ftp
[php_pdo_sqlsrv]
extension=pdo_sqlsrv

Note: On some old servers, the path C:\Program Files (x86)\Plesk\ needs to be replaced by C:\Program Files (x86)\Parallels\Plesk\ in the file. Also, verify that all the paths listed above inside the file do exist.