这是代码：
<?php
function f($b) {
echo xdebug_debug_zval('b');
}
function g() {
echo xdebug_debug_zval('a');
}
$a = 10;
f($a);
f(&$a);
g();
echo xdebug_debug_zval('a');
?>
输出是：
b: (refcount=3, is_ref=0)=10
b: (refcount=3, is_ref=1)=10
a: (refcount=1, is_ref=0)=10
a: (refcount=1, is_ref=0)=10
因此，问题是：为什么它不在b: (refcount=2,..)输出的前两行？
请注意，由于在内部传递变量，不应添加额外的引用xdebug_debug_zval，因为 (1) 变量实际上并未传递，并且 (2) http://www.xdebug.org/docs/上的文档all_functions明确表示：
void xdebug_debug_zval( [string varname [, ...]] )显示有关变量的信息
此函数显示有关一个或多个变量的结构化信息，包括其类型、值和引用计数信息。使用值递归地探索数组。该函数的实现方式与 PHP 的 debug_zval_dump() 函数不同，以便解决该函数所存在的问题，因为变量本身实际上是传递给函数的。Xdebug 的版本更好，因为它使用变量名在内部符号表中查找变量并直接访问所有属性，而无需处理实际将变量传递给函数的问题。结果是这个函数返回的信息比 PHP 自己的显示 zval 信息的函数要准确得多。
是必须处理 XDebug 参数还是 XDebug 本身的怪癖？
PS我phpinfo()的是（PHP 5.3.3，XDebug 2.1.1，Ubuntu 10.10）：
phpinfo()
PHP Version => 5.3.3-1ubuntu9.5
System => Linux ubuntu1010 2.6.35-22-generic #33-Ubuntu SMP Sun Sep 19 20:34:50 UTC 2010 i686
Build Date => May 3 2011 00:47:16
Server API => Command Line Interface
Virtual Directory Support => disabled
Configuration File (php.ini) Path => /etc/php5/cli
Loaded Configuration File => /etc/php5/cli/php.ini
Scan this dir for additional .ini files => /etc/php5/cli/conf.d
Additional .ini files parsed => /etc/php5/cli/conf.d/mysql.ini,
/etc/php5/cli/conf.d/mysqli.ini,
/etc/php5/cli/conf.d/pdo.ini,
/etc/php5/cli/conf.d/pdo_mysql.ini
PHP API => 20090626
PHP Extension => 20090626
Zend Extension => 220090626
Zend Extension Build => API220090626,NTS
PHP Extension Build => API20090626,NTS
Debug Build => no
Thread Safety => disabled
Zend Memory Manager => enabled
Zend Multibyte Support => disabled
IPv6 Support => enabled
Registered PHP Streams => https, ftps, compress.zlib, compress.bzip2, php, file, glob, data, http, ftp, phar, zip
Registered Stream Socket Transports => tcp, udp, unix, udg, ssl, sslv3, sslv2, tls
Registered Stream Filters => zlib.*, bzip2.*, convert.iconv.*, string.rot13, string.toupper, string.tolower, string.strip_tags, convert.*, consumed, dechunk
This server is protected with the Suhosin Patch 0.9.9.1
Copyright (c) 2006-2007 Hardened-PHP Project
Copyright (c) 2007-2009 SektionEins GmbH
This program makes use of the Zend Scripting Language Engine:
Zend Engine v2.3.0, Copyright (c) 1998-2010 Zend Technologies
with Xdebug v2.1.1, Copyright (c) 2002-2011, by Derick Rethans
_______________________________________________________________________
Configuration
bcmath
BCMath support => enabled
Directive => Local Value => Master Value
bcmath.scale => 0 => 0
bz2
BZip2 Support => Enabled
Stream Wrapper support => compress.bz2://
Stream Filter support => bzip2.decompress, bzip2.compress
BZip2 Version => 1.0.5, 10-Dec-2007
calendar
Calendar support => enabled
Core
PHP Version => 5.3.3-1ubuntu9.5
Directive => Local Value => Master Value
allow_call_time_pass_reference => Off => Off
allow_url_fopen => On => On
allow_url_include => Off => Off
always_populate_raw_post_data => Off => Off
arg_separator.input => & => &
arg_separator.output => & => &
asp_tags => Off => Off
auto_append_file => no value => no value
auto_globals_jit => On => On
auto_prepend_file => no value => no value
browscap => no value => no value
default_charset => no value => no value
default_mimetype => text/html => text/html
define_syslog_variables => Off => Off
disable_classes => no value => no value
disable_functions => no value => no value
display_errors => Off => Off
display_startup_errors => Off => Off
doc_root => no value => no value
docref_ext => no value => no value
docref_root => no value => no value
enable_dl => Off => Off
error_append_string => no value => no value
error_log => no value => no value
error_prepend_string => no value => no value
error_reporting => 22527 => 22527
exit_on_timeout => Off => Off
expose_php => On => On
extension_dir => /usr/lib/php5/20090626+lfs => /usr/lib/php5/20090626+lfs
file_uploads => On => On
highlight.bg => <font style="color: #FFFFFF">#FFFFFF</font> => <font style="color: #FFFFFF">#FFFFFF</font>
highlight.comment => <font style="color: #FF8000">#FF8000</font> => <font style="color: #FF8000">#FF8000</font>
highlight.default => <font style="color: #0000BB">#0000BB</font> => <font style="color: #0000BB">#0000BB</font>
highlight.html => <font style="color: #000000">#000000</font> => <font style="color: #000000">#000000</font>
highlight.keyword => <font style="color: #007700">#007700</font> => <font style="color: #007700">#007700</font>
highlight.string => <font style="color: #DD0000">#DD0000</font> => <font style="color: #DD0000">#DD0000</font>
html_errors => Off => Off
ignore_repeated_errors => Off => Off
ignore_repeated_source => Off => Off
ignore_user_abort => Off => Off
implicit_flush => On => On
include_path => .:/usr/share/php:/usr/share/pear => .:/usr/share/php:/usr/share/pear
log_errors => On => On
log_errors_max_len => 1024 => 1024
magic_quotes_gpc => Off => Off
magic_quotes_runtime => Off => Off
magic_quotes_sybase => Off => Off
mail.add_x_header => On => On
mail.force_extra_parameters => no value => no value
mail.log => no value => no value
max_execution_time => 0 => 0
max_file_uploads => 20 => 20
max_input_nesting_level => 64 => 64
max_input_time => -1 => -1
memory_limit => -1 => -1
open_basedir => no value => no value
output_buffering => 0 => 0
output_handler => no value => no value
post_max_size => 8M => 8M
precision => 14 => 14
realpath_cache_size => 16K => 16K
realpath_cache_ttl => 120 => 120
register_argc_argv => On => On
register_globals => Off => Off
register_long_arrays => Off => Off
report_memleaks => On => On
report_zend_debug => Off => Off
request_order => GP => GP
safe_mode => Off => Off
safe_mode_exec_dir => no value => no value
safe_mode_gid => Off => Off
safe_mode_include_dir => no value => no value
sendmail_from => no value => no value
sendmail_path => /usr/sbin/sendmail -t -i => /usr/sbin/sendmail -t -i
serialize_precision => 100 => 100
short_open_tag => On => On
SMTP => localhost => localhost
smtp_port => 25 => 25
sql.safe_mode => Off => Off
track_errors => Off => Off
unserialize_callback_func => no value => no value
upload_max_filesize => 2M => 2M
upload_tmp_dir => no value => no value
user_dir => no value => no value
user_ini.cache_ttl => 300 => 300
user_ini.filename => .user.ini => .user.ini
variables_order => GPCS => GPCS
xmlrpc_error_number => 0 => 0
xmlrpc_errors => Off => Off
y2k_compliance => On => On
zend.enable_gc => On => On
ctype
ctype functions => enabled
date
date/time support => enabled
"Olson" Timezone Database Version => 0.system
Timezone Database => internal
Default timezone => Europe/Moscow
Directive => Local Value => Master Value
date.default_latitude => 31.7667 => 31.7667
date.default_longitude => 35.2333 => 35.2333
date.sunrise_zenith => 90.583333 => 90.583333
date.sunset_zenith => 90.583333 => 90.583333
date.timezone => no value => no value
dba
DBA support => enabled
Supported handlers => cdb cdb_make db4 inifile flatfile
Directive => Local Value => Master Value
dba.default_handler => flatfile => flatfile
dom
DOM/XML => enabled
DOM/XML API Version => 20031129
libxml Version => 2.7.7
HTML Support => enabled
XPath Support => enabled
XPointer Support => enabled
Schema Support => enabled
RelaxNG Support => enabled
ereg
Regex Library => Bundled library enabled
exif
EXIF Support => enabled
EXIF Version => 1.4 $Id: exif.c 293036 2010-01-03 09:23:27Z sebastian $
Supported EXIF Version => 0220
Supported filetypes => JPEG,TIFF
Directive => Local Value => Master Value
exif.decode_jis_intel => JIS => JIS
exif.decode_jis_motorola => JIS => JIS
exif.decode_unicode_intel => UCS-2LE => UCS-2LE
exif.decode_unicode_motorola => UCS-2BE => UCS-2BE
exif.encode_jis => no value => no value
exif.encode_unicode => ISO-8859-15 => ISO-8859-15
fileinfo
fileinfo support => enabled
version => 1.0.5-dev
filter
Input Validation and Filtering => enabled
Revision => $Revision: 298196 $
Directive => Local Value => Master Value
filter.default => unsafe_raw => unsafe_raw
filter.default_flags => no value => no value
ftp
FTP support => enabled
gettext
GetText Support => enabled
hash
hash support => enabled
Hashing Engines => md2 md4 md5 sha1 sha224 sha256 sha384 sha512 ripemd128 ripemd160 ripemd256 ripemd320 whirlpool tiger128,3 tiger160,3 tiger192,3 tiger128,4 tiger160,4 tiger192,4 snefru snefru256 gost adler32 crc32 crc32b salsa10 salsa20 haval128,3 haval160,3 haval192,3 haval224,3 haval256,3 haval128,4 haval160,4 haval192,4 haval224,4 haval256,4 haval128,5 haval160,5 haval192,5 haval224,5 haval256,5
iconv
iconv support => enabled
iconv implementation => glibc
iconv library version => 2.12.1
Directive => Local Value => Master Value
iconv.input_encoding => ISO-8859-1 => ISO-8859-1
iconv.internal_encoding => ISO-8859-1 => ISO-8859-1
iconv.output_encoding => ISO-8859-1 => ISO-8859-1
json
json support => enabled
json version => 1.2.1
libxml
libXML support => active
libXML Compiled Version => 2.7.7
libXML Loaded Version => 20707
libXML streams => enabled
mbstring
Multibyte Support => enabled
Multibyte string engine => libmbfl
HTTP input encoding translation => disabled
mbstring extension makes use of "streamable kanji code filter and converter", which is distributed under the GNU Lesser General Public License version 2.1.
Multibyte (japanese) regex support => enabled
Multibyte regex (oniguruma) backtrack check => On
Multibyte regex (oniguruma) version => 4.7.1
Directive => Local Value => Master Value
mbstring.detect_order => no value => no value
mbstring.encoding_translation => Off => Off
mbstring.func_overload => 0 => 0
mbstring.http_input => pass => pass
mbstring.http_output => pass => pass
mbstring.http_output_conv_mimetypes => ^(text/|application/xhtml\+xml) => ^(text/|application/xhtml\+xml)
mbstring.internal_encoding => no value => no value
mbstring.language => neutral => neutral
mbstring.strict_detection => Off => Off
mbstring.substitute_character => no value => no value
mhash
MHASH support => Enabled
MHASH API Version => Emulated Support
mysql
MySQL Support => enabled
Active Persistent Links => 0
Active Links => 0
Client API version => 5.1.49
MYSQL_MODULE_TYPE => external
MYSQL_SOCKET => /var/run/mysqld/mysqld.sock
MYSQL_INCLUDE => -I/usr/include/mysql
MYSQL_LIBS => -L/usr/lib -lmysqlclient_r
Directive => Local Value => Master Value
mysql.allow_local_infile => On => On
mysql.allow_persistent => On => On
mysql.connect_timeout => 60 => 60
mysql.default_host => no value => no value
mysql.default_password => no value => no value
mysql.default_port => no value => no value
mysql.default_socket => /var/run/mysqld/mysqld.sock => /var/run/mysqld/mysqld.sock
mysql.default_user => no value => no value
mysql.max_links => Unlimited => Unlimited
mysql.max_persistent => Unlimited => Unlimited
mysql.trace_mode => Off => Off
mysqli
MysqlI Support => enabled
Client API library version => 5.1.49
Active Persistent Links => 0
Inactive Persistent Links => 0
Active Links => 0
Client API header version => 5.1.49
MYSQLI_SOCKET => /var/run/mysqld/mysqld.sock
Directive => Local Value => Master Value
mysqli.allow_local_infile => On => On
mysqli.allow_persistent => On => On
mysqli.default_host => no value => no value
mysqli.default_port => 3306 => 3306
mysqli.default_pw => no value => no value
mysqli.default_socket => no value => no value
mysqli.default_user => no value => no value
mysqli.max_links => Unlimited => Unlimited
mysqli.max_persistent => Unlimited => Unlimited
mysqli.reconnect => Off => Off
openssl
OpenSSL support => enabled
OpenSSL Library Version => OpenSSL 0.9.8o 01 Jun 2010
OpenSSL Header Version => OpenSSL 0.9.8o 01 Jun 2010
pcntl
pcntl support => enabled
pcre
PCRE (Perl Compatible Regular Expressions) Support => enabled
PCRE Library Version => 8.02 2010-03-19
Directive => Local Value => Master Value
pcre.backtrack_limit => 100000 => 100000
pcre.recursion_limit => 100000 => 100000
PDO
PDO support => enabled
PDO drivers => mysql
pdo_mysql
PDO Driver for MySQL => enabled
Client API version => 5.1.49
Phar
Phar: PHP Archive support => enabled
Phar EXT version => 2.0.1
Phar API version => 1.1.1
SVN revision => $Revision: 298908 $
Phar-based phar archives => enabled
Tar-based phar archives => enabled
ZIP-based phar archives => enabled
gzip compression => enabled
bzip2 compression => enabled
OpenSSL support => enabled
Phar based on pear/PHP_Archive, original concept by Davey Shafik.
Phar fully realized by Gregory Beaver and Marcus Boerger.
Portions of tar implementation Copyright (c) 2003-2009 Tim Kientzle.
Directive => Local Value => Master Value
phar.cache_list => no value => no value
phar.readonly => On => On
phar.require_hash => On => On
posix
Revision => $Revision: 300764 $
Reflection
Reflection => enabled
Version => $Revision: 300393 $
session
Session Support => enabled
Registered save handlers => files user
Registered serializer handlers => php php_binary wddx
Directive => Local Value => Master Value
session.auto_start => Off => Off
session.bug_compat_42 => Off => Off
session.bug_compat_warn => Off => Off
session.cache_expire => 180 => 180
session.cache_limiter => nocache => nocache
session.cookie_domain => no value => no value
session.cookie_httponly => Off => Off
session.cookie_lifetime => 0 => 0
session.cookie_path => / => /
session.cookie_secure => Off => Off
session.entropy_file => no value => no value
session.entropy_length => 0 => 0
session.gc_divisor => 1000 => 1000
session.gc_maxlifetime => 1440 => 1440
session.gc_probability => 1 => 1
session.hash_bits_per_character => 5 => 5
session.hash_function => 0 => 0
session.name => PHPSESSID => PHPSESSID
session.referer_check => no value => no value
session.save_handler => files => files
session.save_path => /var/lib/php5 => /var/lib/php5
session.serialize_handler => php => php
session.use_cookies => On => On
session.use_only_cookies => On => On
session.use_trans_sid => 0 => 0
shmop
shmop support => enabled
SimpleXML
Simplexml support => enabled
Revision => $Revision: 299424 $
Schema support => enabled
soap
Soap Client => enabled
Soap Server => enabled
Directive => Local Value => Master Value
soap.wsdl_cache => 1 => 1
soap.wsdl_cache_dir => /tmp => /tmp
soap.wsdl_cache_enabled => 1 => 1
soap.wsdl_cache_limit => 5 => 5
soap.wsdl_cache_ttl => 86400 => 86400
sockets
Sockets Support => enabled
SPL
SPL support => enabled
Interfaces => Countable, OuterIterator, RecursiveIterator, SeekableIterator, SplObserver, SplSubject
Classes => AppendIterator, ArrayIterator, ArrayObject, BadFunctionCallException, BadMethodCallException, CachingIterator, DirectoryIterator, DomainException, EmptyIterator, FilesystemIterator, FilterIterator, GlobIterator, InfiniteIterator, InvalidArgumentException, IteratorIterator, LengthException, LimitIterator, LogicException, MultipleIterator, NoRewindIterator, OutOfBoundsException, OutOfRangeException, OverflowException, ParentIterator, RangeException, RecursiveArrayIterator, RecursiveCachingIterator, RecursiveDirectoryIterator, RecursiveFilterIterator, RecursiveIteratorIterator, RecursiveRegexIterator, RecursiveTreeIterator, RegexIterator, RuntimeException, SplDoublyLinkedList, SplFileInfo, SplFileObject, SplFixedArray, SplHeap, SplMinHeap, SplMaxHeap, SplObjectStorage, SplPriorityQueue, SplQueue, SplStack, SplTempFileObject, UnderflowException, UnexpectedValueException
standard
Dynamic Library Support => enabled
Path to sendmail => /usr/sbin/sendmail -t -i
Directive => Local Value => Master Value
assert.active => 1 => 1
assert.bail => 0 => 0
assert.callback => no value => no value
assert.quiet_eval => 0 => 0
assert.warning => 1 => 1
auto_detect_line_endings => 0 => 0
default_socket_timeout => 60 => 60
safe_mode_allowed_env_vars => PHP_ => PHP_
safe_mode_protected_env_vars => LD_LIBRARY_PATH => LD_LIBRARY_PATH
url_rewriter.tags => a=href,area=href,frame=src,input=src,form=fakeentry => a=href,area=href,frame=src,input=src,form=fakeentry
user_agent => no value => no value
sysvmsg
sysvmsg support => enabled
Revision => $Revision: 293036 $
tokenizer
Tokenizer Support => enabled
vld
vld support => enabled
Directive => Local Value => Master Value
vld.active => 0 => 0
vld.col_sep => =>
vld.dump_paths => 1 => 1
vld.execute => 1 => 1
vld.format => 0 => 0
vld.save_dir => /tmp => /tmp
vld.save_paths => 0 => 0
vld.skip_append => 0 => 0
vld.skip_prepend => 0 => 0
vld.verbosity => 1 => 1
wddx
WDDX Support => enabled
WDDX Session Serializer => enabled
xdebug
xdebug support => enabled
Version => 2.1.1
Supported protocols => Revision
DBGp - Common DeBuGger Protocol => $Revision: 1.145 $
Directive => Local Value => Master Value
xdebug.auto_trace => Off => Off
xdebug.collect_assignments => Off => Off
xdebug.collect_includes => On => On
xdebug.collect_params => 0 => 0
xdebug.collect_return => Off => Off
xdebug.collect_vars => Off => Off
xdebug.default_enable => On => On
xdebug.dump.COOKIE => no value => no value
xdebug.dump.ENV => no value => no value
xdebug.dump.FILES => no value => no value
xdebug.dump.GET => no value => no value
xdebug.dump.POST => no value => no value
xdebug.dump.REQUEST => no value => no value
xdebug.dump.SERVER => no value => no value
xdebug.dump.SESSION => no value => no value
xdebug.dump_globals => On => On
xdebug.dump_once => On => On
xdebug.dump_undefined => Off => Off
xdebug.extended_info => On => On
xdebug.file_link_format => no value => no value
xdebug.idekey => no value => no value
xdebug.manual_url => http://www.php.net => http://www.php.net
xdebug.max_nesting_level => 100 => 100
xdebug.overload_var_dump => On => On
xdebug.profiler_aggregate => Off => Off
xdebug.profiler_append => Off => Off
xdebug.profiler_enable => Off => Off
xdebug.profiler_enable_trigger => Off => Off
xdebug.profiler_output_dir => /tmp => /tmp
xdebug.profiler_output_name => cachegrind.out.%p => cachegrind.out.%p
xdebug.remote_autostart => Off => Off
xdebug.remote_connect_back => Off => Off
xdebug.remote_cookie_expire_time => 3600 => 3600
xdebug.remote_enable => Off => Off
xdebug.remote_handler => dbgp => dbgp
xdebug.remote_host => localhost => localhost
xdebug.remote_log => no value => no value
xdebug.remote_mode => req => req
xdebug.remote_port => 9000 => 9000
xdebug.scream => Off => Off
xdebug.show_exception_trace => Off => Off
xdebug.show_local_vars => Off => Off
xdebug.show_mem_delta => Off => Off
xdebug.trace_format => 0 => 0
xdebug.trace_options => 0 => 0
xdebug.trace_output_dir => /tmp => /tmp
xdebug.trace_output_name => trace.%c => trace.%c
xdebug.var_display_max_children => 128 => 128
xdebug.var_display_max_data => 512 => 512
xdebug.var_display_max_depth => 3 => 3
xml
XML Support => active
XML Namespace Support => active
libxml2 Version => 2.7.7
xmlreader
XMLReader => enabled
xmlwriter
XMLWriter => enabled
zip
Zip => enabled
Extension Version => $Id: php_zip.c 300470 2010-06-15 18:48:33Z pajoye $
Zip version => 1.9.1
Libzip version => 0.9.0
zlib
ZLib Support => enabled
Stream Wrapper support => compress.zlib://
Stream Filter support => zlib.inflate, zlib.deflate
Compiled Version => 1.2.1.1
Linked Version => 1.2.3.4
Directive => Local Value => Master Value
zlib.output_compression => Off => Off
zlib.output_compression_level => -1 => -1
zlib.output_handler => no value => no value
Additional Modules
Module Name
readline
sysvsem
sysvshm
Environment
Variable => Value
APACHE_RUN_DIR => /var/run/apache2
APACHE_PID_FILE => /var/run/apache2.pid
PATH => /usr/local/bin:/usr/bin:/bin
APACHE_LOCK_DIR => /var/lock/apache2
LANG => C
APACHE_RUN_USER => www-data
APACHE_RUN_GROUP => www-data
APACHE_LOG_DIR => /var/log/apache2
PWD => /var/www/testme
PHP Variables
Variable => Value
_SERVER["APACHE_RUN_DIR"] => /var/run/apache2
_SERVER["APACHE_PID_FILE"] => /var/run/apache2.pid
_SERVER["PATH"] => /usr/local/bin:/usr/bin:/bin
_SERVER["APACHE_LOCK_DIR"] => /var/lock/apache2
_SERVER["LANG"] => C
_SERVER["APACHE_RUN_USER"] => www-data
_SERVER["APACHE_RUN_GROUP"] => www-data
_SERVER["APACHE_LOG_DIR"] => /var/log/apache2
_SERVER["PWD"] => /var/www/testme
_SERVER["PHP_SELF"] => /tmp/tmp_php_src.txt
_SERVER["SCRIPT_NAME"] => /tmp/tmp_php_src.txt
_SERVER["SCRIPT_FILENAME"] => /tmp/tmp_php_src.txt
_SERVER["PATH_TRANSLATED"] => /tmp/tmp_php_src.txt
_SERVER["DOCUMENT_ROOT"] =>
_SERVER["REQUEST_TIME"] => 1305793398
_SERVER["argv"] => Array
(
[0] => /tmp/tmp_php_src.txt
)
_SERVER["argc"] => 1
PHP License
This program is free software; you can redistribute it and/or modify
it under the terms of the PHP License as published by the PHP Group
and included in the distribution in the file: LICENSE
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
If you did not receive a copy of the PHP license, or have any
questions about PHP licensing, please contact license@php.net.