If * is used for width/precision in printf, then the width/precision
is provided by a printf argument instead of being part of the format
string. Semantics generally match those of printf in C.
This can be used to easily reproduce PHP's float printing behavior:
// Locale-sensitive using precision ini setting.
// Used prior to PHP 8.0.
sprintf("%.*G", (int) ini_get('precision'), $float);
// Locale-insensitive using precision ini setting.
// Used since to PHP 8.0.
sprintf("%.*H", (int) ini_get('precision'), $float);
// Locale-insensitive using serialize_precision ini setting.
// Used in serialize(), json_encode() etc.
sprintf("%.*H", (int) ini_get('serialize_precision'), $float);
Closes GH-5432.
Nikita Popov