phpは配列からランダムにいくつかの重複しない要素を選択する方法です。

/*

 * $array = the array to be filtered

 * $total = the maximum number of items to return

 * $unique = whether or not to remove duplicates before getting a random list

 */

function unique_array($array, $total, $unique = true){

    $newArray = array();

    if((bool)$unique){

        $array = array_unique($array);

    }

    shuffle($array);

    $length = count($array);

    for($i = 0; $i < $total; $i++){

        if($i < $length){

            $newArray[] = $array[$i];

        }

    }

    return $newArray;

}

$phrases = array('Hello Sailor','Acid Test','Bear Garden','Botch A Job','Dark Horse',

    'In The Red','Man Up','Pan Out','Quid Pro Quo','Rub It In','Turncoat',

    'Yes Man','All Wet','Bag Lady','Bean Feast','Big Wig', 'Big Wig','Bear Garden'

    ,'All Wet','Quid Pro Quo','Rub It In');

print_r(unique_array($phrases, 1));

// Returns 1 result

print_r(unique_array($phrases, 5));

// Returns 5 unique results

print_r(unique_array($phrases, 5, false));

// Returns 5 results, but may have duplicates if

// there are duplicates in original array

print_r(unique_array($phrases, 100));

// Returns 100 unique results    

print_r(unique_array($phrases, 100, false));

// Returns 100 results, but may have duplicates if

// there are duplicates in original array