Indentation inside of anonymous functions deletes code

When `indent-tabs-mode` is enabled and a `tab-width` of 4, trying to indent a statement inside an anonymous function deletes some characters.

``` php
foo(function ($bar) {
test('baz');
});
```

With the cursor before `test`, pressing tab changes the line to

``` php
foo(function ($bar) {
t('baz');
});
```

The number of characters deleted seems to depend on the value of `tab-width`. With the brace on a newline, the problem doesn't occur

``` php
foo(function ($bar)
{
test('baz');
});
```

`php-mode-coding-style` is `pear`, but not set in my configuration, so it's just using the default. Running `php-enable-pear-coding-style` manually, then enabling `indent-tabs-mode` again seems to fix the issue in the buffer.