为什么count（false）在PHP中返回1？ [重复]

How does count(false) === 1 make any sense at all since count(null) === 0?

count — Count all elements in an array, or something in an object. -http://php.net/manual/en/function.count.php

This makes even less sense since booleans are primitives and not arrays or countables.

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count returns the number of elements. false is one element (a boolean) but null is nothing, null is not a value.

Note that you can destroy a variable, for example an item in an array by setting it to null:

$a = array(1,2,3);
$a[1] = null;
var_dump(isset($a[1]));

You will obtain false because $a[1] is no longer defined.

If you do the same with false:

$a = array(1,2,3);
$a[1] = false;
var_dump(isset($a[1]));

You will obtain true because $a[1] is set to the boolean false