What is the php array subscript?

PHP array subscript is a unique identifier used to identify array elements. In PHP, arrays can be accessed using numeric subscripts or string subscripts. The subscript of the array can be any integer or string.

For numeric subscripts, PHP will automatically convert the subscript type to an integer type. For example, if the subscript is "1.23", it will be converted to the integer 1. PHP also provides other types of array subscripts, such as Boolean types, which will be converted to 1 (true) or 0 (false).

For string subscripts, PHP will automatically try to convert them into legal identifiers. A legal identifier must begin with a letter or underscore and can be followed by any number of letters, numbers, and underscores. If the string cannot be converted to a legal identifier, it is converted to a numeric subscript.

PHP also supports multi-dimensional arrays. The subscripts of multi-dimensional arrays can use arrays, objects, resources and other types. For example, you can use an array subscript as the subscript of another array, as follows:

$array1 = array('foo', 'bar');
$array2 = array('hello', 'world');
$array3 = array($array1, $array2);
echo $array3[0][1];  //输出bar

In this example, $array3 is an array containing two elements, each element is an array. The first element is $array1 and the second element is $array2. We can use $array30 to access the second element (string) of the first element (array).

In short, PHP array subscript is to identify the unique element in an array. It can be a numerical subscript or a string subscript, or it can be a subscript of a multi-dimensional array. Note that when using string subscripts, make sure they can be converted to legal identifiers.

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