Input multiple field array, how to integrate to the back end?

<input name="f1[]" class="">
<input name="f2[]" class="">
<input name="f3[]" class="">
<input name="f4[]" class="">
<input name="f5[]" class="">

suppose there are five fields.
I can add each row through append, like this:

the number next to the pineapple is related to the pineapple
and so on
how can I catch the pineapple at the back end and output the number on the right into a piece of data?

Mysql php7 php javascript jquery

Nov.15,2021

all use one-dimensional array, and you are welcome to add one-dimensional array.

<head>
    <meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
</head>
<form action="./index.php" method="POST">
    <div>
        <input type="text" name="f[0][0]">
        <input type="text" name="f[0][1]">
        <input type="text" name="f[0][2]">
        <input type="text" name="f[0][3]">
        <input type="text" name="f[0][4]">
    </div>
    <div>
        <input type="text" name="f[1][0]">
        <input type="text" name="f[1][1]">
        <input type="text" name="f[1][2]">
        <input type="text" name="f[1][3]">
        <input type="text" name="f[1][4]">
    </div>
    <input type="submit" value="">
</form>

 <?php
 echo json_encode($_POST);

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