PHP: Notes on `finally`
Published the 2021-03-30

Because PHP has a mix of ambiguous low-level errors and higher-level exceptions in its standard library, and the different mechanisms are not well-documented, I took some notes after trying various cases.
This is done in a `set_error_handler`-free context.

I tested the following cases, even the obvious ones.

- Nothing happening
- Exception thrown
- Warning raised
- Error raised
- Assertion raised
- `goto` used to jump out of the block

## Nothing happening

In case a piece of code in a `try` block runs just fine, the `finally` block is properly executed.

```php
try {
    $meow = 1 + 2;
} finally {
    echo "FINALLY: MEOW\n";
}
```

## Exception thrown

As before, in case anything resembling a `Throwable` is raised within a `try` context, the `finally` block is properly executed.

```php
try {
    throw new Error('ERROR: MEOW');
} finally {
    echo "FINALLY: MEOW\n";
}
```

## Warning raised

When a method within a `try` context raises a `WARNING` of any nature (user or system), the `finally` block is properly executed.

```php
try {
    trigger_error('MEOW MEOW', E_USER_WARNING);
} finally {
    echo "FINALLY: MEOW\n";
}
```

Keep in mind that, by default, a `WARNING` being raised doesn't interrupt the runtime or the currently run block.

```php
try {
    trigger_error('MEOW MEOW', E_USER_WARNING);
    // Will be executed
    $meow = 1 + 2;
} finally {
    echo "FINALLY: MEOW\n";
}
```

## Error raised

When a method within a `try` context raises an `ERROR` of any nature (user or system), the `finally` block is skipped, and the whole runtime stops.

```php
try {
    trigger_error('MEOW MEOW', E_USER_ERROR);
} finally {
    // Will never be reached
    echo "FINALLY: MEOW\n";
}
```

## Assertion raised

When an assertion within a `try` context fails, the `finally` block is skipped, and the whole runtime stops.

```php
try {
    assert(false);
} finally {
    // Will never be reached
    echo "FINALLY: MEOW\n";
}
```

## `goto` used to jump out of the block

As expected of `goto`, if you use this instruction to jump to an arbitrary location of code outside of the reach of the `finally` block, it will be skipped.

```php
try {
    goto meow;
} finally {
    // Will never be reached
    echo "FINALLY: MEOW\n";
}
meow:
echo "GOTO: MEOW\n";
```