A "Locale" is an identifier used to get language, culture, or regionally-specific behavior from an API. PHP locales are organized and identified the same way that the CLDR locales used by ICU (and many vendors of Unix-like operating systems, the Mac, Java, and so forth) use. Locales are identified using RFC 4646 language tags (which use hyphen, not underscore) in addition to the more traditional underscore-using identifiers. Unless otherwise noted the functions in this class are tolerant of both formats.
Examples of identifiers include:
The Locale class (and related procedural functions) are used to interact with locale identifiers--to verify that an ID is well-formed, valid, etc. The extensions used by CLDR in UAX #35 (and inherited by ICU) are valid and used wherever they would be in ICU normally.
Locales cannot be instantiated as objects. All of the functions/methods provided are static.
The null or empty string obtains the "root" locale. The "root" locale is equivalent to "en_US_POSIX" in CLDR. Language tags (and thus locale identifiers) are case insensitive. There exists a canonicalization function to make case match the specification.
These constants describe the choice of the locale for getLocalte method of different classes.