putenv

(PHP 4, PHP 5)

putenv — Sets the value of an environment variable

说明

bool putenv ( string $setting )

Adds setting to the server environment. The environment variable will only exist for the duration of the current request. At the end of the request the environment is restored to its original state.

Setting certain environment variables may be a potential security breach. The safe_mode_allowed_env_vars directive contains a comma-delimited list of prefixes. In Safe Mode, the user may only alter environment variables whose names begin with the prefixes supplied by this directive. By default, users will only be able to set environment variables that begin with PHP_ (e.g. PHP_FOO=BAR). Note: if this directive is empty, PHP will let the user modify ANY environment variable!

The safe_mode_protected_env_vars directive contains a comma-delimited list of environment variables, that the end user won't be able to change using putenv(). These variables will be protected even if safe_mode_allowed_env_vars is set to allow to change them.

参数

setting: The setting, like "FOO=BAR"

返回值

成功时返回 TRUE，或者在失败时返回 FALSE.

范例

Example #1 Setting an environment variable


<?php
putenv("UNIQID=$uniqid");
?>

注释

Warning

The safe_mode_allowed_env_vars and safe_mode_protected_env_vars directives only take effect when safe_mode is enabled.

参见

getenv() - Gets the value of an environment variable

PHP手册 - N: Sets the value of an environment variable

用户评论:

Anonymous Coder (28-Mar-2012 02:28)

It's the putenv() type of environment variables that get passed to a child process executed via exec(). If you need to delete an existing environment variable so the child process does not see it, use: putenv('FOOBAR'); That is, leave out both the "=" and a value.

simon at systemparadox dot co dot uk (24-Feb-2011 01:23)

It seems that putenv() doesn't work when using virtual() to call CGI's. The environment variables don't carry over to the CGI. Try apache_setenv() instead.

php at keith tyler dot com (22-Jun-2010 01:52)

putenv/getenv, $_ENV, and phpinfo(INFO_ENVIRONMENT) are three completely distinct environment stores. doing putenv("x=y") does not affect $_ENV; but also doing $_ENV["x"]="y" likewise does not affect getenv("x"). And neither affect what is returned in phpinfo(). Assuming the USER environment variable is defined as "dave" before running the following: <?php print "env is: ".$_ENV["USER"]."\n"; print "(doing: putenv fred)\n"; putenv("USER=fred"); print "env is: ".$_ENV["USER"]."\n"; print "getenv is: ".getenv("USER")."\n"; print "(doing: set _env barney)\n"; $_ENV["USER"]="barney"; print "getenv is: ".getenv("USER")."\n"; print "env is: ".$_ENV["USER"]."\n"; phpinfo(INFO_ENVIRONMENT); ?> prints: env is: dave (doing: putenv fred) env is: dave getenv is: fred (doing: set _env barney) getenv is: fred env is: barney phpinfo() Environment Variable => Value ... USER => dave ...

JM (17-Feb-2007 02:41)

The other problem with the code from av01 at bugfix dot cc is that the behaviour is as per the comments here, not there: <?php putenv('MYVAR='); // set MYVAR to an empty value. It is in the environment putenv('MYVAR'); // unset MYVAR. It is removed from the environment ?>

povaddict (05-Jun-2006 01:18)

av01 at bugfix dot cc: "putenv('MYVAR='); // unset, otherwise this will pass when run the next time" it won't pass when run next time, "At the end of the request the environment is restored to its original state."

av01 at bugfix dot cc (03-Oct-2005 03:32)

Please be aware, that using putenv() does NOT effect the superglobal $_ENV[] variable. If you want to, set it seperately <?php putenv('MYVAR=hello'); assert(getenv('MYVAR') == 'hello'); // passes assert($_ENV['MYVAR'] == 'hello'); // fails! putenv('MYVAR='); // unset, otherwise this will pass when run the next time ?>

Iavor (07-Feb-2005 10:06)

Compare to apache_setenv() and apache_getenv(). I had a case setting an env var in VirtualHost which I tried to change with putenv() - but did not work. apache_setenv() worked.

cap at capsi dot com (28-Mar-2003 06:18)

I've been using putenv with PHP 4.3.1 and Apache 2.0.44, but it does not seem to restore variables correctly. I'm getting +0100 and -0800 entries all across my Apache logs. Manually adding a putenv in page footers to restore the original value seems to fix things, but I still wish I could set the time zone for a specific request only. I'm not sure whether using putenv affects all threads within the process, that could be another problem.

verkoop at it-design dot com (08-Mar-2001 11:19)

for those who have problems with the putenv ('TZ=Europe/Amsterdam'). I found that there is a solution/work-a-round. It will work, but only if you add mktime(0,0,0,1,1,1970) on the next line. So: <?php putenv ('TZ=Europe/Amsterdam'); mktime(0,0,0,1,1,1970) echo date("H:i:s"); ?>

david dot boyce at messagingdirect dot comnospam (14-Sep-2000 06:23)

Environment variables are part of the underlying operating system's way of doing things, and are used to pass information between a parent process and its child, as well as to affect the way some internal functions behave. They should not be regarded as ordinary PHP variables. A primary purpose of setting environment variables in a PHP script is so that they are available to processes invoked by that script using e.g. the system() function, and it's unlikely that they would need to be changed for other reasons. For example, if a particular system command required a special value of the environment variable LD_LIBRARY_PATH to execute successfully, then the following code might be used on a *NIX system: <?php $saved = getenv("LD_LIBRARY_PATH"); // save old value $newld = "/extra/library/dir:/another/path/to/lib"; // extra paths to add if ($saved) { $newld .= ":$saved"; } // append old paths if any putenv("LD_LIBRARY_PATH=$newld"); // set new value system("mycommand -with args"); // do system command; // mycommand is loaded using // libs in the new path list putenv("LD_LIBRARY_PATH=$saved"); // restore old value ?> It will usually be appropriate to restore the old value after use; LD_LIBRARY_PATH is a particularly good example of a variable which it is important to restore immediately, as it is used by internal functions. If php.ini configuration allows, the values of environment variables are made available as PHP global variables on entry to a script, but these global variables are merely copies and do not track the actual environment variables once the script is entered. Changing $REMOTE_ADDR (or even $HTTP_ENV_VARS["REMOTE_ADDR"]) should not be expected to affect the actual environment variable; this is why putenv() is needed. Finally, do not rely on environment variables maintaining the same value from one script invocation to the next, especially if you have used putenv(). The result depends on many factors, such as CGI vs apache module, and the exact way in which the environment is manipulated before entering the script.