PHP Unconference Europe 2015

putenv

(PHP 4, PHP 5)

putenvFixe la valeur d'une variable d'environnement

Description

bool putenv ( string $setting )

Fixe la valeur d'une variable d'environnement. Cette valeur n'existera que durant la vie du script courant, et l'environnement initial sera restauré lorsque le script sera terminé.

Modifier la valeur de certaines variables système peut être un trou de sécurité considérable. La directive de configuration safe_mode_allowed_env_vars contient une liste de préfixes, séparés par des virgules. Lorsque le Safe Mode est actif, l'utilisateur ne peut que modifier les variables dont le nom commence par les préfixes fournis par cette directive. Par défaut, les utilisateurs ne peuvent modifier que les variables qui commencent par PHP_ (i.e. PHP_FOO=BAR). Note : Si cette directive est vide, PHP autorisera la modification de TOUTES les variables d'environnement !

La directive de configuration safe_mode_protected_env_vars contient une liste de variables d'environnement, séparées par des virgules. Les utilisateurs ne pourront pas modifier ces variables avec la fonction putenv(). Ces variables seront protégées même si safe_mode_allowed_env_vars permet leur modification.

Liste de paramètres

setting

La configuration, comme "FOO=BAR"

Valeurs de retour

Cette fonction retourne TRUE en cas de succès ou FALSE si une erreur survient.

Exemples

Exemple #1 Modification d'une variable d'environnement

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

Notes

Avertissement

Les directives safe_mode_allowed_env_vars et safe_mode_protected_env_vars ne prennent effets que si le safe_mode est activé.

Voir aussi

  • getenv() - Retourne la valeur d'une variable d'environnement

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User Contributed Notes 6 notes

up
5
JM
7 years ago
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
?>
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2
david dot boyce at messagingdirect dot comnospam
14 years ago
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.
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1
php at keith tyler dot com
4 years ago
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
...
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0
Anonymous Coder
2 years ago
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.
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0
Iavor
9 years ago
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.
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-2
cap at capsi dot com
11 years ago
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.
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