php 如果键在变量中，PHP如何从数组中获取值
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PHP how to get value from array if key is in a variable
提问by Mazatec
I have a key stored in a variable like so:
我有一个存储在变量中的密钥，如下所示：
$key = 4;
I tried to get the relevant value like so:
我试图像这样获得相关的价值：
$value = $array[$key];
but it failed. Help.
但它失败了。帮助。
回答by Sarfraz
Your code seems to be fine, make sure that key you specify really exists in the array or such key has a value in your arrayeg:
您的代码似乎没问题，请确保您指定的键确实存在于数组中，或者此类键在您的数组中具有值，例如：
$array = array(4 => 'Hello There');
print_r(array_keys($array));
// or better
print_r($array);
Output:
输出：
Array
(
[0] => 4
)
Now:
现在：
$key = 4;
$value = $array[$key];
print $value;
Output:
输出：
Hello There
回答by code_burgar
$value = ( array_key_exists($key, $array) && !empty($array[$key]) )
? $array[$key]
: 'non-existant or empty value key';
回答by sab0t
As others stated, it's likely failing because the requested key doesn't exist in the array. I have a helper function here that takes the array, the suspected key, as well as a default return in the event the key does not exist.
正如其他人所说，它可能会失败，因为数组中不存在请求的键。我在这里有一个辅助函数，它接受数组、可疑的键，以及在键不存在的情况下的默认返回。
protected function _getArrayValue($array, $key, $default = null)
{
if (isset($array[$key])) return $array[$key];
return $default;
}
hope it helps.
希望能帮助到你。
回答by Gumbo
It should work the way you intended.
它应该按照您的预期工作。
$array = array('value-0', 'value-1', 'value-2', 'value-3', 'value-4', 'value-5' /* … */);
$key = 4;
$value = $array[$key];
echo $value; // value-4
But maybe there is no element with the key 4. If you want to get the fiveth item no matter what key it has, you can use array_slice:
但也许 key 没有元素4。如果你想得到第五个项目，不管它有什么键，你可以使用array_slice：
$value = array_slice($array, 4, 1);
