Types of PHP arrays - associative arrays

Types of PHP arrays - associative array

What is an associative array in PHP?

In the previous article, we introduced "Types of PHP arrays-numeric index array". Today we will introduce associative arrays in detail.

In addition to array index arrays, PHP also has an associative array. In other computer languages, it is generally called hash or map

Using associative arrays, we can specify a keyword for each array element , we call it key

$info = [    'name' => 'andy',     'age' => 18,     'gender' => 'male'];

is equivalent to

$info = array(    'name' => 'andy',     'age' => 18,     'gender' => 'male');

It is impossible to obtain data using numerical subscripts in associative arrays, such as $info[ 0] is empty, we need to use the key as the subscript. The value of $info['age'] is 18.

The key names of associative arrays can be a mixture of numbers and strings, unlike the key names of numeric index arrays which can only be numbers. In an array, as long as one of the key names is not a number, then the array is called an associative array.

Associative arrays are similar to arrays and consist of fields and methods with names as keys.

It contains scalar data, which can be selected individually by index value. Unlike arrays, the index value of an associative array is not a non-negative integer but an arbitrary scalar. These scalars are called Keys and can later be used to retrieve values ​​in the array.

The elements of an associative array are in no particular order, you can think of them as a set of cards. The upper half of each card is the index and the lower half is the numerical value.

The essence of a JavaScript object is an associative array.

Associative arrays (associative arrays) use string indexes (or keys) to access the values ​​of each element stored in the array. The key values ​​​​are as shown in the following table. Associatively indexed arrays are useful for database layer interactions.

Associative array case is as follows:

<?php
$newarray=array("first"=>1,"second"=>2,"third"=>3);
echo $newarray["second"];
$newarray["third"]=8;
echo $newarray["third"];
?>

The output result is:

Tip: The key name of the associative array can be any integer or string. If the key name is a string, don’t forget to add a delimiter to the key name or index—single quote (') or double quote ("). For numeric index arrays, in order to avoid unnecessary trouble, we also recommend It’s better to add delimiters!

In the next article, we will explain "PHP Array Types-Multidimensional Arrays"!

[Related Tutorial Recommendations]

1. Recommended related topics: "php array (Array)"

2. Recommended related video courses:

《Use for loop to traverse arrays: index and associative array》

《 Use while loop to traverse arrays: index and associative array》

《Use foreach loop to traverse: index and associative array》

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