add to array if it isn't there already

Question

How do I add elements to an array only if they aren\'t in there already? I have the following:

$a=array();
// organize the array
foreach($array as $k=>$v)         


        

Answer 1

Taking Gumbo's idea, making the code work:

$array = array('111111','222222','3333333','4444','5555', 
'AAAAAA', 'BBBBBB', 'CCC', 'DDDDDDD', 'EEEEEEEE', 'FFFFFF', 'GGG',
'AAAAAA', 'BBBBBB', 'CCC', 'DDDDDDD', 'EEEEEEEE', 'FFFFFF', 'GGG',
'222222', 
'666666', '777777', 'HHHH');

print_r($array);

$keys= array();
foreach ($array as $k => $v){
    if (isset($v['value'])) {
        $keys[$v] = $k;
    }
}
$unique = array();
foreach ($keys as $key) {
    $unique[] = $array[$key];
}
print "

";
print_r($unique);

Gives this:

Array
(
    [0] => 111111
    [1] => 222222
    [2] => 3333333
    [3] => 4444
    [4] => 5555
    [5] => AAAAAA
    [6] => BBBBBB
    [7] => CCC
    [8] => DDDDDDD
    [9] => EEEEEEEE
    [10] => FFFFFF
    [11] => GGG
    [12] => AAAAAA
    [13] => BBBBBB
    [14] => CCC
    [15] => DDDDDDD
    [16] => EEEEEEEE
    [17] => FFFFFF
    [18] => GGG
    [19] => 222222
    [20] => 666666
    [21] => 777777
    [22] => HHHH
)

Array
(
    [0] => 111111
    [1] => 222222
    [2] => 3333333
    [3] => 4444
    [4] => 5555
    [5] => AAAAAA
    [6] => BBBBBB
    [7] => CCC
    [8] => DDDDDDD
    [9] => EEEEEEEE
    [10] => FFFFFF
    [11] => GGG
    [12] => 666666
    [13] => 777777
    [14] => HHHH
)