To fix this issues you would not change
$this->output .= $this->$rule[‘key’]($rule).”\n”;
to
$this->output .= $this->$rule[‘key’][$rule].”\n”;

rather you would change
$this->output .= $this->$rule[‘key’]($rule).”\n”;
to
$this->output .= $this->{ $rule[‘key’] } ($rule).”\n”;

The first options changes the meaning of enfold’s code and can cause more problems. The problem that php7 is that it is evaulating the following phrase $this->$rule[‘key’]($rule) as $this->{$rule}[”key’] instead of $this->{ $rule[‘key’] }. The curly braces define the order of evaluation. So putting curly braces around the statement $rule[‘key’] will force php the use the string instance instead of the whole array.