What is the difference between associative array and index array in php

The difference between associative arrays and index arrays in php: the subscript (key name) of the index array consists of numbers, and each number corresponds to the position of an array element in the array; while the subscript (key name) of the associative array name) consists of a quoted string, which can be a mixture of numbers and characters, or any integer value or string.

In PHP, an array is a collection of data that forms an operable whole. Each data is an element, and the element contains a key name and a key value.

The difference between index array and associative array is distinguished by key name

1. Index array

Index array The subscript (key name) consists of numbers, starting from 0 by default. Each number corresponds to the position of an array element in the array. There is no need to specify it. PHP will automatically assign an integer value to the key name of the index array, and then start from this The value starts to increment automatically.

<?php     $arr = array(&#39;华为&#39;,&#39;三星&#39;,&#39;vivo&#39;,&#39;oppo&#39;);
    print_r($arr);
    echo &#39;<br/><br><br>';
    echo '数组 $arr 中的，键名为2的键值为：'.$arr[2];
?>

The result is displayed:

You can also write this:

<?php     $arr1 = array(&#39;0&#39; => '苹果','1' => '香蕉','2' => '橘子','3' => '李子','4' => '草莓');
    print_r($arr1);
    echo '<br><br>';
    $arr2[0] = '苹果';
    $arr2[1] = '香蕉';
    $arr2[2] = '橘子';
    $arr2[3] = '李子';
    $arr2[4] = '草莓';
    print_r($arr2);
?>

The result is displayed:

二, Associative array

The subscript (key name) of an associative array is composed of a mixture of numerical values ​​and strings. If a key name in an array is not a number, then the array is an associative array.

<?php     $arr1 = array(&#39;Apple&#39; => '苹果','Banana' => '香蕉','Orange' => '橘子','Plum' => '李子','Strawberry' => '草莓');
    print_r($arr1);
?>

The key name of an associative array can be any integer or string. If the key name is a string, add a delimiting modifier to the key name - single quotes ' ' or double quotes " ". For indexed arrays, in order to avoid confusion, it is best to add delimiters.

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