This API is part of the Hack Standard Library, not HHVM itself.
Facebook Engineer?

This function is available as Str\splice() in Facebook's www repository.

Return the string with a slice specified by the offset/length replaced by the given replacement string


namespace HH\Lib\Str;

function splice(
  string $string,
  string $replacement,
  int $offset,
  ?int $length = null,
): string;

If the length is omitted or exceeds the upper bound of the string, the remainder of the string will be replaced. If the length is zero, the replacement will be inserted at the offset.

Previously known in PHP as substr_replace.


  • string $string
  • string $replacement
  • int $offset
  • ?int $length = null