How can the combination of trim(), maxlength attribute, and mb_substr function be used to ensure input validation and length restrictions?

To ensure input validation and length restrictions, we can combine the trim() function to remove any leading or trailing whitespace, the maxlength attribute in HTML to limit the input length, and the mb_substr() function in PHP to further restrict the input length if needed. This combination helps to sanitize the input data and enforce length restrictions to prevent potential security vulnerabilities or data integrity issues.

$input = trim($_POST['input']); // Remove leading and trailing whitespace
$max_length = 50; // Set maximum input length
$input = mb_substr($input, 0, $max_length); // Limit input length using mb_substr

// Use $input for further processing or validation