Because my home is rather big, creating a new environment fails:

Symfony\Component\Process\Exception\ProcessTimedOutException
The process "find ~/ -name ".pearrc"" exceeded the timeout of 60 seconds.

What is the purpose of searching the whole home directory recursively for this rc file? Wouldn't it be enough to check if it exists within the home directory itself? - If this is the case maybe the following could be a replacement to "find":

$process = $this->getProcess("ls \"~/.pearrc\"");
$process->run();
if ($process->isSuccessful()) { ... }

Because "ls" prints in any case something to stdout, we have to look at the return value. "ls" returns 0 if the file is found (otherwise something else).
Or, to completely get rid of system dependent processes, one could use the filesystem api provided by symfony.