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This article mainly explains "what is the use of PHP associative arrays". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn "what is the use of PHP associative arrays"?

Associative array

An associative array with a value associated with each ID key. It is not best to use numeric arrays when storing data about specific named values. By associating arrays, we can use values as keys and assign values to them.

Here are 10 techniques for manipulating PHP associative arrays, which can help you improve your development efficiency.

1. Add array elements

PHP is a weakly typed language, which means that you don't need to declare an array and its size. Instead, you can declare and populate the array at the same time.

$capitals = array ('Alabama' = >' Montgomery', 'Alaska' = >' Juneau', 'Arizona' = >' Phoenix')

Additional array elements can be appended as follows:

$capitals ['Arkansas'] =' Little Rock'

If you are working with numeric indexed arrays, you may want to use display named functions to prefix and append elements, such as the array_push () and array_unshift () functions, but these functions cannot manipulate associative arrays.

2. Delete array elements

If you want to remove an element from the array, use the unset () function, such as:

Unset ($capitals ['California'])

When using numerically indexed arrays, there are more ways to delete array elements, and you can use the array_shift () and array_pop () functions to delete an element from the beginning and end of the array, respectively.

3. Swap keys and values

Suppose you want to create a new array called $states, using the state capital as the index and the state name as the associated value, which is easy to do using the array_flip () function.

$capitals = array ('Alabama' = >' Montgomery', 'Alaska' = >' Juneau', 'Arizona' = >' Phoenix'); $states = array_flip ($capitals); / / $states = array (/ / 'Montgomery' = > string' Alabama', / / 'Juneau' = > string' Alaska', / / 'Phoenix' = > string' Arizona' / /)

4. Merge arrays

Assuming that the previous array is used by a Web-based "FlashCard" service, and you want to provide a way to test students' knowledge of state capitals in the United States, you can use the array_merge () function to merge arrays containing states and capitals.

$stateCapitals = array ('Alabama' = >' Montgomery', 'Alaska' = >' Juneau', 'Arizona' = >' Phoenix'); $countryCapitals = array ('Australia' = >' Canberra', 'Austria' = >' Vienna', 'Algeria' = >' Algiers'); $capitals = array_merge ($stateCapitals, $countryCapitals)

5. Edit array values

Assuming that the data in the array contains case errors and you want to correct these errors before inserting them into the database, you can use the array_map () function to apply a callback to each array element.

Function capitalize ($element) {$element = strtolower ($element); return ucwords ($element);} $capitals = array ('Alabama' = >' montGoMEry', 'Alaska' = >' Juneau', 'Arizona' = >' phoeniX'); $capitals = array_map ("capitalize", $capitals)

6. Press the key to sort the array

FlashCard programs often use various sorts, such as sorting alphabetically, and you can use the ksort () function to press the key to sort the associative array.

$capitals = array ('Arizona' = >' Phoenix', 'Alaska' = >' Juneau', 'Alabama' = >' Montgomery'); ksort ($capitals)

Because the array is passed to the ksort () function by argument, it means that you no longer need to assign the sort result to another variable.

7. Random array sorting

Another random sorting technique is also involved in the FlashCard program, when you use the shuffle () function to achieve random sorting of array items.

$capitals = array ('Arizona' = >' Phoenix', 'Alaska' = >' Juneau', 'Alabama' = >' Montgomery'); shuffle ($capitals)

If you don't need to disturb the array order and you just want to choose a value at random, use the array_rand () function.

8. Determine whether keys and values exist

You can use the in_array () function to determine whether an array element exists.

Capitals = array ('Arizona' = >' Phoenix', 'Alaska' = >' Juneau', 'Alabama' = >' Montgomery'); if (in_array ("Juneau", $capitals)) {echo "Exists!";} else {echo "Does not exist!";}

Few people know that this function can also determine the existence of an array key, which is the same function as the array_key_exists () function.

Capitals = array ('Arizona' = >' Phoenix', 'Alaska' = >' Juneau', 'Alabama' = >' Montgomery'); if (array_key_exists ("Alaska", $capitals)) {echo "Key exists!";} else {echo "Key does not exist!";}

9. Search the array

You may want to search for array resources so that users can easily retrieve associated states with a specific state capital, and do array search through the array_search () function.

$capitals = array ('Arizona' = >' Phoenix', 'Alaska' = >' Juneau', 'Alabama' = >' Montgomery'); $state = array_search ('Juneau', $capitals); / / $state =' Alaska'

10. Standard PHP library

The standard PHP library (Standard PHP Library,SPL) provides developers with many data structures, iterators, interfaces, exceptions, and other features that were not previously available in the PHP language, which can be used to traverse arrays through object-oriented syntax.

$capitals = array ('Arizona' = >' Phoenix', 'Alaska' = >' Juneau', 'Alabama' = >' Montgomery'); $arrayObject = new ArrayObject ($capitals); foreach ($arrayObject as $state = > $capital) {printf ("The capital of% s is% s", $state, $capital) } / / The capital of Arizona is Phoenix / / The capital of Alaska is Juneau / / The capital of Alabama is Montgomery here, I believe you have a deeper understanding of "what is the use of PHP associative arrays". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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