Pclose docs says it returns true if successful, false otherwise.
In reality it returns the exit status.
Reproduce with:

echo "/bin/true=", pclose(popen("/bin/true", "w")), "\n";
echo "/bin/false=", pclose(popen("/bin/false", "w")), "\n";

This produces:
/bin/true=0
/bin/false=65280

Documentation says that both should return a true value (non-zero).