[RESOLVED] Quick way to determine if array contains ONLY nulls?

Joseph_Sliker · Feb 24, 2009

Hi;

Say I've got 2 simple arrays like

$array1=array(a=>0, b=>, c=>, d=>, e=>); //contains a single value of zero

and

$array2=array(a=>, b=>, c=>, d=>, e=>); //contains only blank/null values

array_sum() will give me a result of "0" for EITHER array, right?

is there a function that will quickly evaluate/differentiate one as having nothing but empty/null keys and the other as having at least ONE actual value...even if it is a zero?

Thanks.

laserlight · Feb 24, 2009

You could always write a function, e.g.,

function containsNonNulls($array) {
    foreach ($array as $value) {
        if (!is_null($value)) {
            return true;
        }
    }
    return false;
}

scrupul0us · Feb 24, 2009


$array1=array('a'=>0, 'b'=>'', 'c'=>'', 'd'=>'', 'e'=>''); //contains a single value of zero
$array2=array('a'=>'', 'b'=>'', 'c'=>'', 'd'=>'', 'e'=>''); //contains only blank/null values

if(!empty($array1))
{
echo 'not empty, ';
}
if(!empty($array2))
{
echo 'not empty, ';
}
if(!is_null($array1))
{
echo 'not null, ';
}
if(is_null($array2))
{
echo 'not null, ';
}
echo array_sum($array1);
echo array_sum($array2);

not empty
not empty
not null
not null

laserlight · Feb 24, 2009

scrupul0us, the empty string is not the same as null, and what Joseph Sliker wants is a way to determine if the array contains a non-null value. However, an array of nulls is not empty.

dagon · Feb 24, 2009

just thinking out loud, would array_search() work?

laserlight · Feb 24, 2009

dagon wrote:
just thinking out loud, would array_search() work?

Considering that my example is just linear search, it just might, assuming that the strict comparison was used.

Joseph_Sliker · Feb 24, 2009

I keep coming back to check this while trying to get laserlight's function suggestion working ( have not done too much with building custom functions.)

Can one put something like "> NULL" or "> ''" into the $needle argument of array_search($needle, $haystack) ?

laserlight · Feb 24, 2009

Joseph Sliker wrote:
Can one put something like "> NULL" or "> ''" into the $needle argument of array_search($needle, $haystack) ?

Oops, I forgot that the linear search is trying to find something that is not present, so array_search() probably will not work since you cannot provide it with a predicate (i.e., the predicate is fixed to check for equality or equivalence).

Just to check: you are trying to determine if an array contains at least one non-null value, right? Because empty strings can produce the same print_r output as in your original example, and that could explain why scrupul0us made his/her suggestion.

scrupul0us · Feb 24, 2009

laserlight;10904362 wrote:
scrupul0us, the empty string is not the same as null, and what Joseph Sliker wants is a way to determine if the array contains a non-null value. However, an array of nulls is not empty.

i know... but he asked what the resultant would be for both so i figured id cover a couple for him

your solution is the best way i can see to do... although if you wanted to be spiffy i suppose you could use array_walk and use a callback no?

NogDog · Feb 24, 2009

Here's a one-liner, just because I could:

function isNullArray($arr)
{
   return(count(array_filter($arr, create_function('$el', 'return(!is_null($el));'))) == 0);
}

scrupul0us · Feb 24, 2009

NogDog;10904384 wrote:

Here's a one-line, just because I could:

function isNullArray($arr)
{
   return(count(array_filter($arr, create_function('$el', 'return(!is_null($el));'))) == 0);
}

:rolleyes: show off

laserlight · Feb 24, 2009

NogDog wrote:
Here's a one-liner, just because I could

That was my first approach, but the bad part is that array_filter() does not terminate early, and Joseph Sliker is apparently concerned about speed.

Joseph_Sliker · Feb 24, 2009

I'm just too thick-headed today to code the function example correctly for my use, but I believe eht following will work:

foreach ($NEWDATA as $id=>$taskscores)
{
$valsearch=""; //used recursively, so clear it out each time.
foreach($taskscores as $key=>$value) 
{$valsearch["$value"]=1;} //just a tally...this is just to create a key value for this variable
ksort($valsearch); //any null keys should not end up in the last position during the next loop.
foreach($valsearch as $key=>$valcount) {$tempkey="$key";} //tempkey just gets overwritten with highest key value  as long as it is empty the save script won't fire	
if($tempkey > "") {echo "<br>$id: there is data...run the save query";
//put the save query code here.
} else {echo "<br>$id: no score data, no save query needed.";}
}

This is for an application where I am entering test scores for a classroom of kids. The submit form contains a line for each kid and a column for each test score (the first level/key of the array is the student id, the second level/key is the id of the task...and the value is the test score.

I just want to do this so that the script won't bother to start running the insert query for lines (kids) for which there was no data entered.

$NEWDATA=Array ( [1111045] => Array ( [1] => [2] => ) [1111055] => Array ( [1] => 0 [2] => 2 ) [1200020] => Array ( [1] => [2] => ) [1200025] => Array ( [1] => [2] => ) )
...When it runs I get this output
1111045: no score data, no save query needed.
1111055: there is data...run the save query
1200020: no score data, no save query needed.
1200025: no score data, no save query needed.

NogDog · Feb 24, 2009

laserlight;10904387 wrote:
That was my first approach, but the bad part is that array_filter() does not terminate early, and Joseph Sliker is apparently concerned about speed.

Yep, yours is faster (and probably easier to maintain, too). And your point is?

:p

Weedpacket · Feb 25, 2009

Another one-liner (because they're out there):

function contains_only_nulls($array)
{
    return count($array) == count(array_keys($array, null, true));
}

laserlight wrote:
That was my first approach, but the bad part is that array_filter() does not terminate early, and Joseph Sliker is apparently concerned about speed.

Presumably there's a threshold array size (which would vary from platform to platform and version to version and all else that isn't equal) between "overhead caused by executing Zend bytecode" and "not terminating early".

Joseph Sliker wrote:

ksort($valsearch); //any null keys should not end up in the last position during the next loop.

Since a linear search is O(n) in the length of the array, while sorting it is going to be O(n log n) in the average case, this is probably going to waste more time than it saves (depending on all the usual overheads).

Though I can't help but wonder how long it would take any of the methods here to save over the others the same amount of time that this thread has occupied

NogDog · Feb 25, 2009

Ooooh...the Weed meister taught me something else new. I've used array_keys() a number of times and never really noticed that 2nd parameter before.

Joseph_Sliker · Feb 25, 2009

From Weedpacket:

Since a linear search is O(n) in the length of the array, while sorting it is going to be O(n log n) in the average case, this is probably going to waste more time than it saves (depending on all the usual overheads).

Dude, I am waaaaaaay out of my depth on that one. But thanks for trying! I'm gonna try and take off the training wheels and build/apply the functions you an lazerlight were kind enough to provide. People are asking me to do so much with my online apps now, I've got to get more efficient with code.

Joseph_Sliker · Feb 25, 2009

Okay...making some progress but:

Given the array:

$NEWDATA=Array ( [1111045] => Array ( [1] => 0 [2] => ) [1111055] => Array ( [1] => [2] => ) [1200020] => Array ( [1] => [2] => 3 ) [1200025] => Array ( [1] => [2] => ) ) ;

My scripting of the Laserlight version

function contains_only_nulls_lazer($array) {
    foreach ($array as $value) {
        if (!is_null($value)) {
            return true;
        }
    }
    return false;
} 

foreach ($NEWDATA as $id=>$testscores)
{
echo "<br>$id: ".call_user_func('contains_only_nulls_lazer',$testscores)."";
}

Gives me this output:

1111045: 1
1111055: 1
1200020: 1
1200025: 1

And the Weedpacket version:

function contains_only_nulls_weedpacket($array)
{
    return count($array) == count(array_keys($array, null, true));
} 

foreach ($NEWDATA as $id=>$testscores)
{
echo "<br>$id: ".call_user_func('contains_only_nulls_weedpacket',$testscores)."";
}

Gets me this:

1111045:
1111055:
1200020:
1200025:

I suspect it may have something to do with my use of call_user_func ... like I say I'm not too familiar with this yet.

Thanks for everyone's help so far.

Joseph_Sliker · Feb 25, 2009

If I modify the weedpacket version thusly,

function contains_only_nulls_weedpacket($array)
{
    return count($array) == count(array_keys($array, '', true)); //changed null to '' (empty string)
}

I now get this output which appears to be on the right track!

1111045:
1111055: 1
1200020:
1200025: 1

Now I just have to figure out how to use this as a trigger for running the insert query.

Joseph_Sliker · Feb 25, 2009

This seems to do the trick:

//define the function
function contains_only_nulls_weedpacket($array)
{return count($array) == count(array_keys($array, '', true));} 


//use the function
foreach ($NEWDATA as $id=>$testscores)
{
echo "<br>$id: ";
if (call_user_func('contains_only_nulls_weedpacket',$testscores)) {echo "NO SCORES";} else {echo "RUN INSERT QUERY";}
}

Thanks everyone!

[RESOLVED] Quick way to determine if array contains ONLY nulls?

JJoseph_Sliker

laserlight

Sscrupul0us

laserlight

Ddagon

laserlight

JJoseph_Sliker

laserlight

Sscrupul0us

NogDog

Sscrupul0us

laserlight

JJoseph_Sliker

NogDog

Weedpacket

NogDog

JJoseph_Sliker

JJoseph_Sliker

JJoseph_Sliker

JJoseph_Sliker