What types of keys can be used in php arrays?

PHP is a high-level programming language, and its powerful array functions make many programmers put it down. Array is a data structure that manages data through key-value pairs. In PHP, the keys of arrays can be of many types. Next, let’s learn about the types of keys of PHP arrays.

1. Integer type

In PHP, integer is a commonly used data type, and integer can also be used as the type of array key. To give a specific example, we can use the following statement to create an array of integer keys:

$array = array(1 => 'one', 2 => 'two', 3 => 'three');

In the above statement, the key values ​​1, 2, and 3 are all integers. We can also access these elements through subscripts:

echo $array[1]; // 输出'one'
echo $array[2]; // 输出'two'
echo $array[3]; // 输出'three'

2. String type

In addition to integer types, the keys of PHP arrays can also be string types. Such arrays are also called associative arrays. We can use string keys to record some data that is completely different from integers.

For example, the following statement creates an array containing string keys:

$array = array('name' => 'John', 'age' => 30, 'gender' => 'male');

In this array, 'name', 'age', and 'gender' are all characters String is also the key of array. We can also use subscripts to access these elements:

echo $array['name']; // 输出'John'
echo $array['age']; // 输出30
echo $array['gender']; // 输出'male'

3. Boolean type

In PHP, Boolean type values ​​can be represented by 0 and 1. PHP array keys can also be of Boolean type. For example, the following statement creates an array containing a Boolean key:

$array = array(true => 'Yes', false => 'No');

In this array, true and false are Boolean values ​​and are also the keys of the array. We can use subscripts to access these elements:

echo $array[true]; // 输出'Yes'
echo $array[false]; // 输出'No'

4. Floating point type

The key of a PHP array can also be a floating point type. This is very similar to an array of integer keys, except that the keys here are of floating point type. For example, the following statement creates an array containing floating-point keys:

$array = array(1.2 => 'one point two', 2.1 => 'two point one', 3.14 => 'pi');

In this array, 1.2, 2.1, and 3.14 are all floating-point numbers and are also the keys of the array. We can also use subscripts to access these elements:

echo $array[1.2]; // 输出'one point two'
echo $array[2.1]; // 输出'two point one'
echo $array[3.14]; // 输出'pi'

5. Object type

In addition to basic data types, the key of a PHP array can also be an object type. This kind of array is called an object array. Object arrays are mainly used to associate objects with other data. For example, the following statement creates an array containing object keys:

$obj1 = new stdClass();
$obj1->name = 'John';
$obj1->age = 30;

$obj2 = new stdClass();
$obj2->name = 'Mary';
$obj2->age = 25;

$array = array($obj1 => 'John', $obj2 => 'Mary');

In this array, $obj1 and $obj2 are both PHP objects and the keys of the array. We can also use subscripts to access these elements:

echo $array[$obj1]; // 输出'John'
echo $array[$obj2]; // 输出'Mary'

Summary

The above is a summary of what types of keys can be used in PHP arrays. PHP programmers can choose different types of keys according to actual needs to achieve the functions they want. It should be noted that the keys of an array can be of multiple types, but you should try to avoid using multiple types of keys in an array at the same time. This will bring great difficulties to the maintenance of the code.

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