php命令：exec 2命令带有1个变量

In php, I have 2 command like that (my wesite run on ubuntu os): cmd1:

exec("tmp=123");

cmd2:

$test = exec('echo $tmp');

Why cmd2 don't know: $tmp. How can I catch $tmp in cmd 1, thanks a lot

exec executes an external program in it's own environment which ceases to exist after the process finishes, if you wish to pass an environment variable to a external program you need to set it using putenv, for example:

putenv('tmp=123'); $test = exec('echo $tmp');

This usage is rather strange though, you may want to re-think your design.