| description | FHIRPath operators, precedence, and language features. |
|---|---|
| icon | code |
FHIRPath expressions navigate and transform FHIR data. They combine path navigation, function calls, and operators. Every expression evaluates against an input collection and produces an output collection.
The evaluator implements arithmetic, comparison, equivalence, logical, string, collection, membership, and type operators.
| Category | Operators | Notes |
|---|---|---|
| Arithmetic | +, -, *, /, div, mod |
div is integer division; mod is remainder |
| Comparison | =, !=, <, >, <=, >= |
|
| Equivalence | ~, !~ |
Equivalence / non-equivalence (tokens EQUIVALENT / NOT_EQUIVALENT) |
| Logical | and, or, xor, implies |
Three-valued logic |
| String | & |
String concatenation |
| Collection | | |
Union |
| Membership | in, contains |
|
| Type | is, as |
Type testing and casting |
{% hint style="info" %}
~ tests equivalence and !~ its negation. Equivalence differs from = by ignoring collection
order and, for strings, case and whitespace.
{% endhint %}
// Comparison and logical
$service->evaluate('age > 18 and status = "active"', $patient);
$service->evaluate('value > 100 or value < 0', $observation);
// Arithmetic (precedence: * / div mod bind tighter than + -)
$service->evaluate('value * 2', $observation);
$service->evaluate('(value + 10) / 2', $observation);
// Membership and union
$service->evaluate('"phone" in telecom.system', $patient);
$service->evaluate('name | telecom', $patient);
// Type operators
$service->evaluate('value is Quantity', $observation);
$service->evaluate('value as Quantity', $observation);The parser and evaluator support the core FHIRPath 2.0 syntax:
| Feature | Example |
|---|---|
| Path navigation | Patient.name.given |
| Indexing | name[0] |
| Function calls | name.where(use = "official") |
| Literals | strings, numbers, booleans, date/time, quantities |
| Collection literals | {} (empty), {1, 2, 3} |
| External constants | %context, %resource, … |
| Reserved identifiers | $this, $index, $total |
The is operator tests whether an item conforms to a named type, and as filters the collection
to items of that type. Temporal values use dedicated types (FHIRPathDate, FHIRPathDateTime,
FHIRPathTime), and decimals use FHIRPathDecimal to preserve precision.
See the Function Reference for the full library of built-in functions,
including type-conversion helpers such as toInteger(), toQuantity(), and ofType().