I have written a PHP application using Windows and XAMPP. I've been trying to run it on Ubuntu 10.10 with Lighttpd 1.4.26. Parts of the application work fine, but whenever I try to log in, I get a 500 - Internal Server Error page.

The only thing that shows up in /var/log/lighttpd/error.log is

2011-02-25 13:43:13: (mod_fastcgi.c.2582) unexpected end-of-file (perhaps the fastcgi process died): pid: 1169 socket: unix:/tmp/php.socket-0 
2011-02-25 13:43:13: (mod_fastcgi.c.3367) response not received, request sent: 1596 on socket: unix:/tmp/php.socket-0 for /~denton/customer-facing-portal/index.php?, closing connection 

If I had any output whatsoever from PHP, this would be a lot easier to debug. Any ideas on how to get some?

Here is my /etc/lighttpd/lighttpd.conf file:

# Debian lighttpd configuration file
#

############ Options you really have to take care of ####################

## modules to load
server.modules = (
            "mod_alias",
            "mod_compress",
#           "mod_rewrite",
#           "mod_redirect",
#           "mod_usertrack",
#           "mod_expire",
#           "mod_flv_streaming",
#           "mod_evasive",
            "mod_setenv"
)

## a static document-root, for virtual-hosting take look at the
## server.virtual-* options
server.document-root       = "/var/www/"

## where to upload files to, purged daily.
server.upload-dirs = ( "/var/cache/lighttpd/uploads" )

## where to send error-messages to
server.errorlog            = "/var/log/lighttpd/error.log"

## files to check for if .../ is requested
index-file.names           = ( "index.php", "index.html",
                               "index.htm", "default.htm",
                               "index.lighttpd.html" )


## Use the "Content-Type" extended attribute to obtain mime type if possible
# mimetype.use-xattr = "enable"

##
# which extensions should not be handle via static-file transfer
#
# .php, .pl, .fcgi are most often handled by mod_fastcgi or mod_cgi
static-file.exclude-extensions = ( ".php", ".pl", ".fcgi" )


######### Options that are good to be but not neccesary to be changed #######

## Use ipv6 only if available. (disabled for while, check #560837)
#include_shell "/usr/share/lighttpd/use-ipv6.pl"

## bind to port (default: 80)
# server.port               = 81

## bind to localhost only (default: all interfaces)
## server.bind                = "localhost"

## error-handler for status 404
#server.error-handler-404  = "/error-handler.html"
#server.error-handler-404  = "/error-handler.php"

## to help the rc.scripts
server.pid-file            = "/var/run/lighttpd.pid"

##
## Format: <errorfile-prefix><status>.html
## -> ..../status-404.html for 'File not found'
#server.errorfile-prefix    = "/var/www/"

## virtual directory listings
dir-listing.encoding        = "utf-8"
server.dir-listing          = "enable"

### only root can use these options
#
# chroot() to directory (default: no chroot() )
#server.chroot            = "/"

## change uid to <uid> (default: don't change)
server.username            = "www-data"

## change gid to <gid> (default: don't change)
server.groupname           = "www-data"

#### compress module
compress.cache-dir          = "/var/cache/lighttpd/compress/"
compress.filetype           = ("text/plain", "text/html", "application/x-javascript", "text/css")

#### url handling modules (rewrite, redirect, access)
# url.rewrite                 = ( "^/$"             => "/server-status" )
# url.redirect                = ( "^/wishlist/(.+)" => "http://www.123.org/$1" )

#### expire module
# expire.url                  = ( "/buggy/" => "access 2 hours", "/asdhas/" => "access plus 1 seconds 2 minutes")

#### external configuration files
## mimetype mapping
include_shell "/usr/share/lighttpd/create-mime.assign.pl"

## load enabled configuration files,
## read /etc/lighttpd/conf-available/README first
include_shell "/usr/share/lighttpd/include-conf-enabled.pl"

## Set environment variables
setenv.add-environment = (
    "DB_URL__DEMO" => "192.168.1.231",
    "DB_NAME_DEMO" => "demo",
    "DB_USER_DEMO" => "user",
    "DB_PASS_DEMO" => "password",
    "DB_AGENCY_DEMO" => "demo"
)

Here is my /etc/php5/cgi/php.ini file (sans 1641 lines of comments):

[PHP]
register_long_arrays = Off
short_open_tag = Off
engine = On
short_open_tag = Off
asp_tags = Off
precision = 14
y2k_compliance = On
output_buffering = 4096
zlib.output_compression = Off
implicit_flush = Off
unserialize_callback_func =
serialize_precision = 100
allow_call_time_pass_reference = Off
safe_mode = Off
safe_mode_gid = Off
safe_mode_include_dir =
safe_mode_exec_dir =
safe_mode_allowed_env_vars = PHP_
safe_mode_protected_env_vars = LD_LIBRARY_PATH
disable_functions =
disable_classes =
expose_php = On
max_execution_time = 30
max_input_time = 60
memory_limit = 128M
error_reporting = E_ALL & ~E_DEPRECATED & ~E_STRICT
display_errors = On
display_startup_errors = On
log_errors = On
log_errors_max_len = 1024
ignore_repeated_errors = Off
ignore_repeated_source = Off
report_memleaks = On
track_errors = On
html_errors = On
variables_order = "GPCS"
request_order = "GP"
register_globals = Off
register_long_arrays = Off
register_argc_argv = Off
auto_globals_jit = On
post_max_size = 8M
magic_quotes_gpc = Off
magic_quotes_runtime = Off
magic_quotes_sybase = Off
auto_prepend_file =
auto_append_file =
default_mimetype = "text/html"
doc_root =
user_dir =
enable_dl = Off
cgi.fix_pathinfo=1
file_uploads = On
upload_max_filesize = 2M
max_file_uploads = 20
allow_url_fopen = On
allow_url_include = Off
default_socket_timeout = 60

[Date]
date.timezone = "America/Chicago"

[filter]
[iconv]
[intl]
[sqlite]
[sqlite3]
[Pcre]
[Pdo]

[Pdo_mysql]
pdo_mysql.cache_size = 2000
pdo_mysql.default_socket=

[Phar]

[Syslog]
define_syslog_variables  = Off

[mail function]
SMTP = localhost
smtp_port = 25
mail.add_x_header = On

[SQL]
sql.safe_mode = Off

[ODBC]
odbc.allow_persistent = On
odbc.check_persistent = On
odbc.max_persistent = -1
odbc.max_links = -1
odbc.defaultlrl = 4096
odbc.defaultbinmode = 1

[Interbase]
ibase.allow_persistent = 1
ibase.max_persistent = -1
ibase.max_links = -1
ibase.timestampformat = "%Y-%m-%d %H:%M:%S"
ibase.dateformat = "%Y-%m-%d"
ibase.timeformat = "%H:%M:%S"

[MySQL]
mysql.allow_local_infile = On
mysql.allow_persistent = On
mysql.cache_size = 2000
mysql.max_persistent = -1
mysql.max_links = -1
mysql.default_port =
mysql.default_socket =
mysql.default_host =
mysql.default_user =
mysql.default_password =
mysql.connect_timeout = 60
mysql.trace_mode = Off

[MySQLi]
mysqli.max_persistent = -1
mysqli.allow_persistent = On
mysqli.max_links = -1
mysqli.cache_size = 2000
mysqli.default_port = 3306
mysqli.default_socket =
mysqli.default_host =
mysqli.default_user =
mysqli.default_pw =
mysqli.reconnect = Off

[mysqlnd]
mysqlnd.collect_statistics = On
mysqlnd.collect_memory_statistics = Off

[OCI8]

[PostgresSQL]
pgsql.allow_persistent = On
pgsql.auto_reset_persistent = Off
pgsql.max_persistent = -1
pgsql.max_links = -1
pgsql.ignore_notice = 0
pgsql.log_notice = 0

[Sybase-CT]
sybct.allow_persistent = On
sybct.max_persistent = -1
sybct.max_links = -1
sybct.min_server_severity = 10
sybct.min_client_severity = 10

[bcmath]
bcmath.scale = 0

[browscap]

[Session]
session.save_handler = files
session.use_cookies = 1
session.use_only_cookies = 1
session.name = PHPSESSID
session.auto_start = 0
session.cookie_lifetime = 0
session.cookie_path = /
session.cookie_domain =
session.cookie_httponly =
session.serialize_handler = php
session.gc_probability = 1
session.gc_divisor = 1000
session.gc_maxlifetime = 1440
session.bug_compat_42 = Off
session.bug_compat_warn = Off
session.referer_check =
session.entropy_length = 0
session.cache_limiter = nocache
session.cache_expire = 180
session.use_trans_sid = 0
session.hash_function = 0
session.hash_bits_per_character = 5
url_rewriter.tags = "a=href,area=href,frame=src,input=src,form=fakeentry"

[MSSQL]
mssql.allow_persistent = On
mssql.max_persistent = -1
mssql.max_links = -1
mssql.min_error_severity = 10
mssql.min_message_severity = 10
mssql.compatability_mode = Off
mssql.secure_connection = Off

[Assertion]
[COM]
[mbstring]
[gd]
[exif]

[Tidy]
tidy.clean_output = Off

[soap]
soap.wsdl_cache_enabled=1
soap.wsdl_cache_dir="/tmp"
soap.wsdl_cache_ttl=86400
soap.wsdl_cache_limit = 5
[sysvshm]

[ldap]
ldap.max_links = -1

[mcrypt]

[dba]

Update: here is /etc/lighttpd/conf-enabled/15-fastcgi-php.conf As far as I know, it's just the default config file the Ubuntu package installed.

## FastCGI programs have the same functionality as CGI programs,
## but are considerably faster through lower interpreter startup
## time and socketed communication
##
## Documentation: /usr/share/doc/lighttpd-doc/fastcgi.txt.gz
##                http://redmine.lighttpd.net/projects/lighttpd/wiki/Docs:ConfigurationOptions#mod_fastcgi-fastcgi

## Start an FastCGI server for php (needs the php5-cgi package)
fastcgi.server += ( ".php" => 
    ((
        "bin-path" => "/usr/bin/php-cgi",
        "socket" => "/tmp/php.socket",
        "max-procs" => 1,
        "idle-timeout" => 20,
        "bin-environment" => ( 
            "PHP_FCGI_CHILDREN" => "4",
            "PHP_FCGI_MAX_REQUESTS" => "10000"
        ),
        "bin-copy-environment" => (
            "PATH", "SHELL", "USER"
        ),
        "broken-scriptfilename" => "enable"
    ))
)