Assignments in Expressions

Convert any assignment to an assignment and a statement. For example:

```php
$a = 1;
if ($a++ > 1) {
   echo 'a is greater than 1';
}
```

Turns into:

```python
a = 1
if a > 1:
  a += 1
```

Some expressions are already translated. It is needed to evaluate every potential place where Python is expecting an expression and if an assignment is found, deal with it. 