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I just want to use array_walk() with ceil() to round all the elements within an array. But it doesn't work.

The code:

$numbs = array(3, 5.5, -10.5); array_walk($numbs, "ceil"); print_r($numbs);

output should be: 3,6,-10

The error message:

Warning: ceil() expects exactly 1 parameter, 2 given on line 2

output is: 3,5.5,-10.5 (Same as before using ceil())

I also tried with round().

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4 Answers 4

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10

Use array_map instead.

$numbs = array(3, 5.5, -10.5); $numbs = array_map("ceil", $numbs); print_r($numbs);

array_walk actually passes 2 parameters to the callback, and some built-in functions don't like being called with too many parameters (there's a note about this on the docs page for array_walk). This is just a Warning though, it's not an error.

array_walk also requires that the first parameter of the callback be a reference if you want it to modify the array. So, ceil() was still being called for each element, but since it didn't take the value as a reference, it didn't update the array.

array_map is better for this situation.

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1 Comment

You're welcome :-) Sometimes one array_* function is better than another, depending on the situation.
2

I had the same problem with another PHP function. You can create "your own ceil function". In that case it is very easy to solve:

function myCeil(&$list){ $list = ceil($list); } $numbs = [3, 5.5, -10.5]; array_walk($numbs, "myCeil"); // $numbs output Array ( [0] => 3 [1] => 6 [2] => -10 )
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2

The reason it doesn't work is because ceil($param) expects only one parameter instead of two.

What you can do: 

$numbs = array(3, 5.5, -10.5); array_walk($numbs, function($item) { echo ceil($item); });

If you want to save these values then go ahead and use array_map which returns an array.

UPDATE

I suggest to read this answer on stackoverflow which explains very well the differences between array_map, array_walk, and array_filter

Hope this helps.

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Not quite. The warning says "ceil() expects exactly 1 parameter, 2 given". array_walk will call your callback function and pass it 2 parameters ($value and $key). The array wasn't getting updated because array_walk will only do that if the $value parameter is a reference (and its value is updated in the callback).
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That is because array_walk needs function which first parameter is a reference & 

function myCeil(&$value){ $value = ceil($value); } $numbs = array(3, 5.5, -10.5); array_walk($numbs, "myCeil"); print_r($numbs);
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