Export a variable from PHP to shell
If you're trying to pass some output to a shell variable, you can do it like this:
$ testvar=$(php -r 'print "hello"')$ echo $testvarhelloShowing how export affects things:
$ php -r '$a=getenv("testvar"); print $a;'$ export testvar$ php -r '$a=getenv("testvar"); print $a;'helloIn these examples, the interactive shell is the parent process and everything else shown is a child (and siblings of each other).
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.