RegExp = #(?:"([^"]+)")|([^ ]+)#

string = apple "banana crust" dandelion elephant "fawn grass" heffalump

matches = Array
(
    [0] => Array
        (
            [0] => apple
            [1] => "banana crust"
            [2] => dandelion
            [3] => elephant
            [4] => "fawn grass"
            [5] => heffalump
        )

    [1] => Array
        (
            [0] => 
            [1] => banana crust
            [2] => 
            [3] => 
            [4] => fawn grass
            [5] => 
        )

    [2] => Array
        (
            [0] => apple
            [1] => 
            [2] => dandelion
            [3] => elephant
            [4] => 
            [5] => heffalump
        )

)
RegExp = #(?:"([^"]+)")|([^ ]+)#

string = apple "banana crust" dandelion elephant "fawn grass" heffalump

preg_split = Array
(
    [0] =>  
    [1] =>  
    [2] =>  
    [3] =>  
    [4] =>  
)