Escape textarea by preserving returning lines.

esc-textarea.php

<?php
/**
 * Escape by preserving the newlines : <br />
 * By applying wp_kses on a textarea
 *
 * @param $string
 *
 * @return mixed
 * @author Maxime CULEA
 */
function mc_esc_textarea( $string ) {
	// Replace <br> <br/> <br > <br /> with %newline%
	$_string = preg_replace( '/(<br\s*\/?>\s*)/mi', "%newline%", $string );
	// Sanitize the textearea
	$_string = wp_kses( $_string, '' );
	// Put back the <br />
	$_string = str_replace( '%newline%', '<br />', $_string );
	// Delete last empty useless characters
	return trim( $_string );
}