What does array_filter without a callback do?

Question

I just came across this code:

array_filter(array_map('intval', $array));

It seems to return all entries of $array converted to int where the number is > 0.

However, I can't see on the manual page that this is defined. It is supposed to return the array value if the callback function evaluates to true. But there isn't any callback function defined here.

Confusing is also that the callback function is optional on the manual page.

array_filter usually just removes empties (or equivalent) in your array if no callback. — Rasclatt
– Rasclatt, Commented Oct 19, 2014 at 21:57
This is extracted from manual If no callback is supplied, all entries of array equal to FALSE (see converting to boolean) will be removed. — King King
– King King, Commented Oct 19, 2014 at 21:59

Stas Sorokin · Accepted Answer · 2020-12-16 12:09:12Z

41

Removes empty or equivalent values from array:

$entry = array(
    0 => 'foo',
    1 => false,
    2 => -1,
    3 => null,
    4 => '',
    5 => 0
);
    
print_r(array_filter($entry));

Result

Array
(
    [0] => foo
    [2] => -1
)

See the original documentation from the manual: Example #2 array_filter() without callback

edited Dec 16, 2020 at 12:09

Stas Sorokin

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answered Oct 19, 2014 at 21:58

Rasclatt

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2 Comments

Peter Mortensen Over a year ago

What is the merit of the approved suggested edit (not a rhetorical question)?

Stas Sorokin Over a year ago

@PeterMortensen I have added a 0 to the $entry array to show that array_filter($entry) function also filters(removes) the value 0 (besides false, null and empty string ' ')

Bob Brown · Accepted Answer · 2014-10-19 21:58:28Z

12

If you read just a little further on the page to which you linked, you find, "If no callback is supplied, all entries of array equal to FALSE (see converting to boolean) will be removed."

answered Oct 19, 2014 at 21:58

Bob Brown

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