What is the subscript of php array

In PHP, array is a very powerful and commonly used data type. The subscript of a PHP array refers to the unique identifier corresponding to each element in the array, which is used to access and modify elements in the array.

In PHP, the subscript of an array can use the following types:

1. Integer subscript: The array subscript can be a positive integer or a negative integer, usually using integer subscript Targets store ordered data, such as daily temperatures over a period of time.
2. String subscript: Array subscript can be a string, usually used to store associative arrays, such as dictionaries, database tables, etc. Note that string subscripts are case-sensitive.
3. Boolean subscript: In PHP, you can use the Boolean type as the array subscript. When the Boolean value is true, the array subscript is 1, otherwise the subscript is 0.
4. Null type subscript: In PHP, you can use null value as array subscript, and the corresponding subscript of null value is 0.

It should be noted that when using a string as an array subscript, if the string is a pure numeric string (such as "123"), PHP will automatically convert it to an integer type subscript.

Here are some common examples of using arrays:

1. Numeric index array:

$nums = array(1, 2, 3, 4, 5);
echo $nums[0]; // 输出1
echo $nums[3]; // 输出4

2. Associative array:

$user = array("name" => "Tom", "age" => 23, "gender" => "male");
echo $user["name"]; // 输出Tom
echo $user["age"]; // 输出23

3. Boolean subscript:

$is_valid = array(true => "valid", false => "invalid");
echo $is_valid[false]; // 输出invalid
echo $is_valid[true]; // 输出valid

4. Empty subscript:

$empty_index = array("" => "empty", null => "null");
echo $empty_index[""]; // 输出empty
echo $empty_index[null]; // 输出null

In short, how many subscripts do PHP arrays have? different types. When using it, developers need to choose different subscript types according to actual needs in order to correctly store and access array elements.

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