Pair¶
A pair is a data structure that holds exactly two related values, often a key and a value, or two correlated items. It is one of the simplest compound data structures.
In PHP, pairs are commonly represented as a two-element indexed array, a two-element associative array, or a simple object with two properties. PHP does not have a built-in pair type, but the Ds\Pair class from the Data Structures extension provides a typed key–value pair.
Pairs appear in many contexts: iterating over associative arrays yields key–value pairs, array_map() with null as the callback zips arrays into indexed pairs, and functions such as array_combine() associate two arrays as paired keys and values.
Pairs are also the basis of more complex structures such as maps and dictionaries.
<?php
// Native: two-element array as a pair
$pair = ['key' => 'value'];
// Ds\Pair from the Data Structures extension
$pair = new \Ds\Pair('name', 'Alice');
echo $pair->key; // name
echo $pair->value; // Alice
// Iterating key-value pairs
$map = ['a' => 1, 'b' => 2];
foreach ($map as $key => $value) {
echo "$key => $value\n";
}
?>
Related : Array, Associative Array, Data Structure, Data Structure, Map
