The "array_fill_keys()" function is used fill an array with values,by specifying the keys.

    array_fill_keys(array,value)

In the above syntax "array" is the array to be filled with the values provided in "value".

    <?php
    $b = array('food', 5, 10, 'bar');
    $a = array_fill_keys($b, 'fruit');
    print_r($a);
    ?>

    Array
     (
      [food]=> fruit
      [5]   => fruit
      [10]  => fruit
      [bar] => fruit
     )

In the above example array is filled for the specified keys. The keys are food, 5, 10, bar, are filled with the string 'fruit'.