CakeFest 2017 NYC, the Official CakePHP Conference


(PHP 4, PHP 5, PHP 7)

putenvImposta il valore di una variabile d'ambiente


void putenv ( string $setting )

Imposta una variable nell'ambiente del server. La variabile d'ambiente esisterà solo per lòa durata dsello script Alla fine di questo l'ambiente sarà ripristinato allo stato originario.

L'impostazione di certe variabili d'ambiente può causare dei problemi di sicurezza. La direttiva safe_mode_allowed_env_vars contiene un'elenco separato da virgole di prefissi. In Mpodlità Sicura, l'utente può soltanto alterare le variabili d'ambiente il cui nome inizia con il prefisso indicato da questa direttiva. Per default, gli utenti sono abilitati ad impostare le variabili d'ambiente con inizino con PHP_ (ad esempio PHP_FOO=BAR). Nota: Se questa direttiva è vuota, il PHP permetterà all'utente di modificare QUALSIASI variabile d'ambiente!

La direttiva safe_mode_protected_env_vars contiene un elenco separato da virgola di variabili d'ambiente, che l'utente non può modificare tramite putenv(). Questa variabili saranno protette anche se safe_mode_allowed_env_vars autorizza la modifica a queste.


Queste impostazioni hanno effetto soltanto se safe-mode è impostato!

Example #1 Impostazione di una variabile d'ambiente


Vedere anche getenv().

add a note add a note

User Contributed Notes 4 notes

php at keith tyler dot com
6 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:

print "env is: ".$_ENV["USER"]."\n";
"(doing: putenv fred)\n";
"env is: ".$_ENV["USER"]."\n";
"getenv is: ".getenv("USER")."\n";
"(doing: set _env barney)\n";
"getenv is: ".getenv("USER")."\n";
"env is: ".$_ENV["USER"]."\n";


env is: dave
(doing: putenv fred)
env is: dave
getenv is: fred
(doing: set _env barney)
getenv is: fred
env is: barney


Variable => Value
USER => dave
10 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:
('MYVAR='); // set MYVAR to an empty value.  It is in the environment
putenv('MYVAR'); // unset MYVAR.  It is removed from the environment
Anonymous Coder
4 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:


That is, leave out both the "=" and a value.
david dot boyce at messagingdirect dot comnospam
16 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

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:

= 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

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.
To Top