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<?php $x = array( '1x', 'fgd', 'fd', 'fg' ); $y = array_keys( $x ); echo debug_zval_dump( $y );
Output for 7.0.0 - 7.1.0
array(4) refcount(2){ [0]=> int(0) [1]=> int(1) [2]=> int(2) [3]=> int(3) }
Output for 4.3.0 - 5.6.28
array(4) refcount(2){ [0]=> long(0) refcount(1) [1]=> long(1) refcount(1) [2]=> long(2) refcount(1) [3]=> long(3) refcount(1) }