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string_cast_for_switch

Note

This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information.

The rules for coercion when doing a comparison where the RHS is a string are complicated and it's not sufficient to just do straight casts on $value

namespace HH\Lib\Legacy_FIXME;

function string_cast_for_switch(
  mixed $value,
  ?arraykey $first_truthy = NULL,
  ?arraykey $first_zeroish = NULL,
  ?arraykey $first_falsy = NULL,
  dict<arraykey, int> $intish_vals = dict [
],
  dict<arraykey, float> $floatish_vals = dict [
],
): string;

Instead, we need to do some data tracking to convert the input to specifics values to match specific cases under different circumstances.

arraykey instead of string for second arg courtesy of non-transparent enums *

Parameters​

  • mixed $value
  • ?arraykey $first_truthy = NULL
  • ?arraykey $first_zeroish = NULL
  • ?arraykey $first_falsy = NULL
  • dict<arraykey, int> $intish_vals = dict [ ]
  • dict<arraykey, float> $floatish_vals = dict [ ]

Returns​

  • string