Export a variable from PHP to shell

Question

I'm trying to set a variable that should be accessible from outside PHP. Ideally this should be a local variable, but environment variables are also welcome.

First, I've tried putenv(), but this gives no result:

$ php -r "putenv('PHP_TEST=string');" ; echo $PHP_TEST

$

When i call getenv() from the same script — it results in the right 'string' value. Safe mode is off, but the manual says 'PHP_' prefix is vital with safe=on so I use it just in case :)

Then I try system() or shell_exec():

$ php -r "shell_exec('PHP_TEST=string');" ; echo $PHP_TEST

$ php -r "shell_exec('export PHP_TEST=string');" ; echo $PHP_TEST

$

Is there a workaround? what might be the reason? I'm using Ubuntu Linux 9.10 "Karmic", but FreeBSD server gives the same result.

Dennis Williamson · Accepted Answer · 2010-01-04 23:41:01Z

3

If you're trying to pass some output to a shell variable, you can do it like this:

$ testvar=$(php -r 'print "hello"')
$ echo $testvar
hello

Showing how export affects things:

$ php -r '$a=getenv("testvar"); print $a;'
$ export testvar
$ php -r '$a=getenv("testvar"); print $a;'
hello

In these examples, the interactive shell is the parent process and everything else shown is a child (and siblings of each other).

answered Jan 4, 2010 at 23:41

Dennis Williamson

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2 Comments

kolypto Over a year ago

Thanks! That makes the question clear. But then, how getopt (and some other non-builtin programs) manage to export variables to the outer context? (E.g. getopt exports $OPTIND)

Dennis Williamson Over a year ago

You're confusing the external /usr/bin/getopt which doesn't and can't do that with the builtin getopts which does.

Brian Agnew · Accepted Answer · 2010-01-04 23:12:36Z

2

Environment variables that are exported are only available in child processes.

So you'll be able to set an environment variable and then spawn a child process. The environment variable will be visible in that child process. However setting it in php and then launching a successive process (echo, in your example above) won't work.

If you set the variable and then spawn/exec a new process, it should be visible in that new process.

answered Jan 4, 2010 at 23:12

Brian Agnew

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