Detailed explanation of key conversion method in php array

Php arrays are important data storage structures, and the use of php arrays is very flexible. Therefore, the understanding of arrays is also very important. In particular, understand the default conversion method of array keys.

1、 Acceptable types of key and value in php array

1. The key can only be an integer or a string. If it is of other types, data type conversion will be performed.

2. Value can be any type.

2、 Type conversion of array key

The key will have the following cast:

1. Integer string will be converted to integer. A string containing a valid integer value is converted to an integer. For example, the key name "8" will actually be saved as 8. However, "08" will not be cast because it is not a legal decimal value.

2. Convert floating point number to integer. Floating point numbers are also converted to integer, meaning that their decimal parts are rounded off. For example, the key 8.7 will actually be saved as 8.

3. Boolean values will also be converted to integer types. That is, the key name true will be saved as 1 and the key name false will be saved as 0.

4. Null will be converted to an empty string, that is, null key name will actually be stored as "".

5. Arrays and objects cannot be used as key names. Otherwise, an error will be reported.

If multiple cells in the array definition use the same key name, only the last one is used, and the previous ones are overwritten.