PHP Tutorials - Herong's Tutorial Examples - v5.13, by Dr. Herong Yang
What Is an Array
This section describes what is an array - an ordered pairs of keys and values. If sequential integer keys are used, an array is a simple indexed list. If string keys are used, an array is a map.
What Is an Array? An array is a data type that represents an ordered pairs of keys and values. Arrays in PHP are different than arrays in most of other languages. Basic rules for PHP's arrays are:
1. An array can be constructed by the array constructor, like:
$myArray = array(k1=>v1, k2=>v2, ..., kn=>vn);
where k1, k2, ..., and kn are keys of integer type or string type. v1, v2, ..., and vn are values of any data types.
2. The value of a given key in an array can be expressed by the array variable followed by the key in square brackets, like:
3. The value of a given key in an array can be modified by an assignment statement, like:
$myArray[kn] = new_value.
4. A new pair of key and value can be added to an array by an assignment statement, like:
$myArray[kx] = vx
5. If a string key represents an integer, it will be used as an integer key. So $myArray['7'] is the same as $myArray.
6. If the key is missing in an array assignment or an array constructor, an integer key of 0, or the highest integer key plus 1, will be provided. So $myArray = "Last" assigns "Last" to a new integer key.
7. An empty string is also a valid string key, like:
$myArray[''] = vy;
8. A pair of key and value can be removed by using the unset() function, like:
9. Pairs of keys and values are ordered in an array like a queue. New pairs are always added at the end of the array.
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