How can I understand the above code? Array_filter

How can I understand the code? Array_filter & lt ;? Php & nbsp; $ arr = array (0, 0, 1, 2, 4); & nbsp; $ arr = array_filter ($ arr); & nbsp; print_r ($ arr );? & Gt; do not need array_f to ask the experts how to understand the code? Array_filter
$ Arr = array (, 2 );
$ Arr = array_filter ($ arr );
Print_r ($ arr );
?>
Is array_filter (array, function) not required )? Does writing an array directly mean that the user-defined function value is zero? Or how to understand it? Please advise

------ Solution --------------------
Array array_filter (array [, callback])

Array_filter () transmits each value in the array to the callback function in sequence. If the callback function returns TRUE, the current value of the array is included in the returned result array. The key name of the array remains unchanged.

If the callback function is not provided, array_filter () deletes all entries in the array that are equal to FALSE.
If the value is false, it is null, false, 0 .......
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Flase false true