Can array keys in PHP be numbers?

In PHP, array is a very important data type because it can be used to store a series of values. In PHP, array keys and values ​​correspond to each other, and we can use keys to access values. In an array, keys can be numbers or strings.

Then the question comes, is the PHP array key number? The answer is: it can be a number or a string.

In PHP, the keys of arrays are also called keywords. Keywords can be numbers, strings, or quoted strings. If a numeric keyword is used, it is automatically converted to the string type. Here are some examples:

// 数字关键字
$numbers = array(
   0 => "zero",
   1 => "one",
   2 => "two"
);

// 字符串关键字
$strings = array(
   "zero" => 0,
   "one" => 1,
   "two" => 2
);

// 带引号的字符串关键字
$quotes = array(
   "zero" => "0",
   "one" => "1",
   "two" => "2"
);

In the above example, we can see that array keys can be numbers, strings, or quoted strings.

When the array key is a number, PHP will convert it to the string type. For example, if you use a number as an array key, you can access the element through the string type. For example:

$numbers = array(
   0 => "zero",
   1 => "one",
   2 => "two"
);

echo $numbers["0"]; // 输出：zero

In this example, we use $numbers["0"] to access the element. Of course, we can also use $numbers[0] to access the element. same element.

So when you use a numeric key, PHP will automatically convert it to string type, so you can access the element via string type or numeric type.

In summary, array keys in PHP can be numbers, strings, or quoted strings, so you can choose the appropriate array key type based on your needs.

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