从数组中删除条目，其值为NULL [NULL]

Possible Duplicate:
remove element from array based on its value?

I have this array

$arr = array(
 'key1'=>'value1',
 'key2'=>NULL,
 'key3'=>'value2'
);

if I do implode(',',$arr); I get: value1,,value2 (notice the empty space)

Is there a way to skip that NULL values? To get something like this:

value1,value2

I could traverse all the array and unset manually the key where the value is NULL, but it's a bit an overkill doens't it?

Edit:

To save time Maybe I could do just one loop to iterate over the array, and in the same loop I check for null values and if isn't null I append it the ','

like this:

foreach($arr as $k=>$v) {
  if ($v !== NULL) {
   echo $v.',';
  }
}

The problem here is that I have a final ',' at the end.

Edit

As gordon asked, it ran this test (1000000 iterations)

First using array_filter:

$pairsCache = array('key1'=>'value1','key2'=>NULL,'key3'=>'value3',
                    'key4'=>'value4','key5'=>'value5');

for($i=0;$i<1000000;$i++) {

    $query = "INSERT INTO tbl (";
    $keys='';
    $values='';

    $pairs = array_filter($pairsCache,function($v){return $v !== NULL;});

    $keys = array_keys($pairs);

    //> keys    
    $query .= implode(',',$keys ) . ") VALUES ( '";

    //> values
    $query .= implode("','",$pairs) . "')";
}

Time: 7.5949399471283
Query: "INSERT INTO tbl (key1,key3,key4,key5) VALUES ( 'value1','value3','value4','value5')"

Second using only one loop:

for($i=0;$i<1000000;$i++) {

    $query = "INSERT INTO tbl (";
    $keys='';
    $values='';

    foreach($pairsCache as $k=>$v) {
        if ($v!==NULL) {

            $keys .= $k.',';
            $values .= "'{$v}',";
        }
     }

    $keys=rtrim($keys,',');
    $values=rtrim($values,',');

    $query = $query . $keys . ') VALUES ( ' . $values . ')';

 }

Time: 4.1640941333771
Query: INSERT INTO tbl (key1,key3,key4,key5,) VALUES ( 'value1','value3','value4','value5')

$arr = array_filter($arr);

array_filter() removes every value, that evaluates to false from $arr.

If you need finer control, you can pass a callback as second argument

arr = array_filter($arr, function ($item) { return !is_null($item);});

At last of course you can iterate over the array yourself

foreach (array_keys($arr) $key) {
  if (is_null($arr[$key])) unset($arr[$key]);
}

Note, that there is no downside, if you filter and output in two separate steps

You can use array_filter():

If no callback is supplied, all entries of input equal to FALSE (see converting to boolean) will be removed.

implode(',', array_filter($arr));

You can simply use bellow code.

Edited.

function nullFilter($val)
{
    return $val !== NULL;
}
$arr = array( 'key1'=>'value1', 'key2'=>NULL, 'key3'=>'value2' );

$filteredArray = array_filter($arr,"nullFilter");

echo implode(',', $filteredArray);

Cheers!

Prasad.

There is no possibility to do this using only implode().

You can traverse all the array (as you said) maybe in a wrapper my_implode() function, or you can use something less elegant such as:

trim(preg_replace('/[,]+/', ',', implode(',', $arr)), ',');