PHP，in_array，0值 [英] Php, in_array, 0 value

问题描述

我是想了解下一个场景的 in_array 行为：

I was trying to understand the in_array behavior at the next scenario:

$arr = array(2 => 'Bye', 52, 77, 3 => 'Hey');
var_dump(in_array(0, $arr));

在 in_array（）的返回值是一个布尔真正。正如你可以看到有否值等于 0 ，所以如果能有一个人，请帮助我理解为什么函数返回真的吗？

The returned value of the in_array() is boolean true. As you can see there is no value equal to 0, so if can some one please help me understand why does the function return true?

推荐答案

这是一个已知的问题，在每次的的文档。请看下面的例子：

This is a known issue, per the comments in the documentation. Consider the following examples:

in_array(0, array(42));      // FALSE
in_array(0, array('42'));    // FALSE
in_array(0, array('Foo'));   // TRUE

要避免这种情况，提供第三放慢参数，真正，将在比较中的严格模式的将不仅是价值，而且种类比较结果为好：

To avoid this, provide the third paramter, true, placing the comparison in strict mode which will not only compare values, but types as well:

var_dump(in_array(0, $arr, true));

其他的变通办法存在不必要每张支票被放置在严格模式：

Other work-arounds exist that don't necessitate every check being placed in strict-mode:

in_array($value, $my_array, empty($value) && $value !== '0');

为什么？

后面所有的的原因是很可能<一个href=\"http://php.net/manual/en/language.types.string.php#language.types.string.conversion\">string-to-number转换的。如果我们试图从再见得到一个数字，我们得到 0 ，这是我们在问到查表的值。

But Why?

The reason behind all of this is likely string-to-number conversions. If we attempt to get a number from "Bye", we are given 0, which is the value we're asking to look-up.

echo intval("Bye"); // 0

要确认这一点，我们可以使用 array_search 找到关联的密钥的匹配的值：

To confirm this, we can use array_search to find the key that is associated with the matching value:

$arr = array(2 => 'Bye', 52, 77, 3 => 'Hey');
echo array_search(0, $arr);

在此，返回的关键是 2 ，这意味着 0 在<$ C的转换被发现$ C>细则为整数。

In this, the returned key is 2, meaning 0 is being found in the conversion of Bye to an integer.

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