> For the complete documentation index, see [llms.txt](https://php-fhir-tools.ardenexal.net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://php-fhir-tools.ardenexal.net/fhirpath/functions/types.md).

# Type Conversion & Checking

## Conversion

Each `toX()` function converts a single-item input to the target type (returning empty when conversion is not possible). Each `convertsToX()` companion returns a Boolean reporting whether the conversion would succeed, without performing it.

| Function                                            | Description                                   | Example                              |
| --------------------------------------------------- | --------------------------------------------- | ------------------------------------ |
| `toBoolean()` / `convertsToBoolean()`               | Convert to / test convertibility to Boolean.  | `'true'.toBoolean()` → `true`        |
| `toInteger()` / `convertsToInteger()`               | Convert to / test convertibility to Integer.  | `'42'.toInteger()` → `42`            |
| `toDecimal()` / `convertsToDecimal()`               | Convert to / test convertibility to Decimal.  | `'3.14'.toDecimal()`                 |
| `toDate()` / `convertsToDate()`                     | Convert to / test convertibility to Date.     | `'2024-01-15'.toDate()`              |
| `toDateTime()` / `convertsToDateTime()`             | Convert to / test convertibility to DateTime. | `'2024-01-15T10:00:00'.toDateTime()` |
| `toTime()` / `convertsToTime()`                     | Convert to / test convertibility to Time.     | `'10:30:00'.toTime()`                |
| `toQuantity([unit])` / `convertsToQuantity([unit])` | Convert to / test convertibility to Quantity. | `'5 mg'.toQuantity()`                |
| `toString()` / `convertsToString()`                 | Convert to / test convertibility to String.   | `(42).toString()` → `'42'`           |

## Checking

| Function       | Description                                                | Example                                 |
| -------------- | ---------------------------------------------------------- | --------------------------------------- |
| `ofType(type)` | Filters the collection to items of the given type.         | `Bundle.entry.resource.ofType(Patient)` |
| `type()`       | Returns type information (namespace + name) for each item. | `Patient.active.type()`                 |

{% hint style="info" %}
Type specifiers accept both the `System.` namespace (e.g. `System.Boolean`) and the `FHIR.` namespace (e.g. `FHIR.Patient`). For runtime type testing with the `is` and `as` operators, see [Expressions & Operators](/fhirpath/expressions.md).
{% endhint %}


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