xml_parser_create_ns is a function in PHP's XML extension that allows handling namespaces while parsing XML. Its function signature is as follows:

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1. Function introduction array_intersect_ukey array_intersect_ukey(array $array1, array $array2, callable $key_compare_func): array This function returns an array that contains all the keys in $array1 that also exist in $array2. The way of comparing the keys is determined by key_compare_func.