WP_List_Util::pluck doesn't support a null $field

[iandunn]

​array_column() accepts a null value for the $column_key parameter. When passed null, it returns the complete array, which is a useful trick for reindexing database results, etc.

$array = [
    [ 'id' => 123, 'name' => 'Joe' ],
    [ 'id' => 345, 'name' => 'Sally' ]
];

array_column( $array, null, 'id' ); // [ 123 => [ 'id' => 123, 'name' => 'Joe'] ...

wp_list_pluck() doesn't work when using that on an object, though:

Warning: Undefined property: stdClass::$ in wp-includes/class-wp-list-util.php on line 185

It seems like array_column() has had support for objects since PHP7, so one way to achieve this might be something like:

if ( version_compare( ... ) {
    return array_column( $this->output, $field, $index_key )
}

// existing code remains as fallback for older versions

It might be good to use something like 7.0.7 to skip a few bugs that were fixed.

[iandunn]

56262.diff​ looks like a good start!

Two helpful improvements could be adding ​unit tests and ​inline docs (adding a @since, updating the $field parameter description, etc).

is_null( $field ) might be more explicit / self documenting than isset(), especially after the $field docs are updated to mention that null can be passed.

Using isset() could also unintentionally hide PHP warnings (and therefore bugs) when devs make a typo in the field name, etc.