What's the Purpose of `[]` in HTML Input Field Names?

Understanding HTML Input Arrays

You're probably familiar with using input fields with the [] notation, like <input name="foo[]" ...>. But what is this called, and is there a specific HTML specification for it?

PHP Input Arrays

Contrary to what you might think, the use of [] in input field names is not an HTML feature. It's actually a PHP convention used to parse field values into an array.

When you submit a form containing input fields with the [] notation, PHP creates an array with the name of the field. For example, if you have:

<input type="checkbox" name="food[]" value="apple" />
<input type="checkbox" name="food[]" value="pear" />

PHP will generate an array called $_POST['food'] containing the selected values. You can access these values using array indices:

echo $_POST['food'][0]; // Output: first checkbox selected

You can also iterate through the array to get all selected values:

foreach( $_POST['food'] as $value ) {
    print $value;
}

Lack of Specific Name

It's worth noting that the use of [] in input field names does not have a specific name in HTML or PHP. It's simply a convention that has become widely used for creating arrays from form input.

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