How to test if array has empty value in it? - php

Question

I have an array that I want to test for empty elements, I have tried using array_walk to walk an array (a single dimension array) and return true if the array of elements (values) has got any empty elements.
I naturally went to the PHP website, looked at the examples on offer and they don't make any sense because it does not give a clear example of how you would use array_walk for this. I tried array_filter and that didn't seem to do much either.
Example of what I was trying to do.
$test = array("Tree"=>"Ash","TreeID"=>"Q23-123","count"=>14,"User"=>"P.Williams");
$result = array_walk( $test, "empty", true );
All I get as a result is "Array".
and PHP parser is having a hissy fit about it, they say clearly, bool array_walk ( array &$array , callable $callback [, mixed $userdata = NULL ] ) in their site, this I deduced to be something $result array_walk ( $theTargetArray, "StringNameOfFunction", theResultIfTure); but nothing is that simple.
So far I have found lots of examples on many sites and it seems that people have just copied and pasted the PHP examples, some have changed their names to hide that they have copied and pasted the example...
Can someone let me know what it is that I am doing wrong here please?
(Also FAO stackoverflow site maintainers, What is the point in suggesting a tag, I click to use it and then I get told I can not create a new tag unless I have 1500 points??? Seriously Why? Good idea if you go and think about that one.)

Answer 1

$my_arr = array(....); // your array here
$has_empty_value = sizeof($my_arr) != sizeof(array_filter($my_arr));

Answer 2

array_walk is not going to help you on that. It's a mutator function, and is intended to change array elements, not to retrieve information about them. What you're looking for is a boolean aggregator function known as any or some in other languages. PHP doesn't provide it out of the box, so you have to write it by hand:
function any($iter, $pred) {
foreach($iter as $item)
if($pred($item))
return true;
return false;
}
However, an attempt to use it with empty, as in
print any($test, 'empty')
will fail, because empty is not a real function and can't be used indirectly. A workaround is to wrap it in yet another function and pass that one to any:
any($test, function($x) { return empty($x); })
Another option is to filter an array through boolval, thus removing "falsy" values, and compare lengths:
$hasEmptyElements = count(array_filter($test, 'boolval')) < count($test);
Note that, unlike any, which is "lazy", filter always processes the whole array.

Answer 3

The docs for array_walk say "Applies the user-defined callback function to each element of the array array." Therefore, you can use it with your own callbacks or with with a closure, like so:
$test = array("Tree"=>"Ash","TreeID"=>"Q23-123", "count"=> 14, "User"=>"P.Williams");
$result = array_walk( $test, function($value) {
return empty($value);
});
Of course, this depends on what you are trying to achieve as this will loop through all the values and $result will be true if all the values are empty but the last one is not.
If you are looking to find out if any of the values are empty, a function that stops after it finds an empty item would be better:
function hasEmptyValues(array $array)
{
foreach ($array as $key => $value) {
if (empty($value)) {
//Empty value found
return true;
}
}
//None of the values are empty
return false;
}