将二维数组合并为一维数组[重复]

What is the best way to merge a 2-dimensional array into a 1-dimensional array?

Source Array:

    $example = array(
        array(
            'red',
            'green'
        ),
        array(
            'blue',
            'brown'
        ),
        array(
            'yellow'
        )
    );

Required Output Array:

    $output = array(
        'red',
        'green',
        'blue',
        'brown',
        'yellow'
    );

Solution that works but I am not sure if it is the most efficient because the use of array_merge in a loop seems to be ugly:

    $output = array();
    foreach($example as $v) {
        array_merge($output , $v);
    }

Is there more efficient way of doing this?

</div>

One liner here is:

$output = call_user_func_array('array_merge', $example);

try this

$result = call_user_func_array('array_merge', $example);
print_r($result);

output will be

Edit As a text output

Array ( [0] => red [1] => green [2] => blue [3] => brown [4] => yellow )

Read more about call_user_func_array