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DocumentationHackReferenceClassHH\ImmVectorfirstKey

HH\ImmVector::firstKey

Returns the first key in the current ImmVector

public function firstKey(): ?int;

Returns

  • ?int - The first key (an integer) in the current ImmVector, or null if the current ImmVector is empty.

Examples

See [Vector::firstKey](</hack/reference/class/Vector/firstKey/#examples>) for usage examples.