Description:
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https://github.com/php/php-langspec/blob/master/spec/12-arrays.md#arrays

 The concept of an array's internal cursor or an object's internal cursor is never mentioned. The state of the internal cursor of an array or object can be witnessed via the current(), key(), next(), prev(), reset(), end(), and each() library functions. While it's technically library functions that expose the state of the cursor to the programmer, you can find code deep in the core array/object implementation of PHP5 that deals with and maintains internal cursors. Also, internal cursors get mentioned in various parts of the php.net documentation, including the documentation for "foreach", so internal cursors are arguably a language feature.