What is the difference between arrays in php7 and php5

The difference between arrays in php7 and php5 is: 1. Long integer key names in PHP7 will be forced to be converted into strings; 2. PHP7 "list()" function is more strict than PHP5, "list()" "The function can only be used for numeric arrays and must be sorted starting from 0; 3. PHP7 array constants are more clear than PHP5. PHP7 uses the "define()" function to define an array constant. Make sure that constants are not modified. Array constants in PHP5 are ambiguous and may change between requests.

# Operating system for this tutorial: Windows 10 system, php7 version, Dell G3 computer.

There are some differences between PHP 7 and PHP 5 arrays in some aspects, including the following points:

1. Long integer key names are now forced to be converted to strings

In PHP 7, if you use a long integer as the key name of the array, the key name will be cast to the string type.

Therefore, in PHP7 $key=1; arr[key] = value; equivalent to $key="1"; arr[key] = value

2, list () Stricter

list() function is used to assign the values ​​in an array to a set of variables. In PHP 7, the list() function can only be used with numeric arrays and must be sorted starting from 0, otherwise a warning or error will be thrown.

3. Array constants are more clear

In PHP 7, you can use the define() function when defining an array constant. Doing this ensures that the constant cannot be modified. In PHP 5, array constants are ambiguous and may change between requests.

The following is a simple example showing how to use the define() function to define and use array constants in PHP 7:

define('MY_ARRAY', [
    'key1' => 'value1',
    'key2' => 'value2'
]);
echo MY_ARRAY['key1']; // 输出：value1

It should be noted that array constants defined in this way can only be used in PHP 5.6.0 or above or PHP 7.0.0 or above can run successfully, otherwise an error will be reported.

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