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What key names can be used in php arrays
- PHPzOriginal
- 2023-04-26 09:21:511597browse
PHP is a popular programming language that is widely used. Among them, array is one of the most basic data types in PHP. An array is a data structure that enables developers to store multiple values in a single variable. In PHP, arrays can use the following key names:
- Numeric Key
Numeric Key is the most commonly used key in PHP arrays. These are the default keys because they are the keys of the first element in the array, starting from 0 and increasing. For example, $arr = array('apple', 'banana', 'orange'); 0, 1 and 2 here are numeric keys.
- String Key
String key refers to a key that can use a string as an array key name. They can be any valid string, for example, $arr= array('name' => 'John', 'age' => 30); where 'name' and 'age' are string keys.
- Multidimensional Key (Multidimensional Key)
Multidimensional array refers to an array that can nest other arrays within an array. This means we can use multiple levels of array keys. For example, $arr = array(
array('apple', 'banana', 'orange'),
array('red', 'green', 'blue')
); 这里的第一层的数组使用数字键，第二层的数组则使用数字键。
- Constants Key
Constant keys refer to keys that can use constants as array key names. Constants are not available when the program is executed. variable values. For example, $arr = array(FRUIT_APPLE => 'apple', FRUIT_BANANA => 'banana'); FRUIT_APPLE and FRUIT_BANANA here are constant keys.
In short, arrays in PHP can Use numeric keys, string keys, multi-dimensional array keys and constant keys. According to development needs, we can choose to use different key name types for different application scenarios.
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