Change

<?php

// Current
public function get_values() {
	foreach ( $this->tabs as $tab => $settings ) {
		foreach ( $settings['fields'] as $fields ) {
			foreach ( (array)$fields as $f ) {
				if ( isset( $f['name'] ) )
					$this->parameters[$f['name']] = $this->get_value($f);
				elseif($f['type'] == 'selects' && isset($f['selects'])) {
					foreach ($f['selects'] as $select) {
						$this->parameters[$select['name']] = $this->get_value($select);
					}
				}elseif($f['type'] == 'checkboxes' && isset($f['options'])) {
					foreach ((array)$f['options'] as $key => $value) {
						$this->parameters[$key] = $this->get_value(array('name' => $key));
					}
				}elseif($f['type'] == 'texts' && isset($f['texts'])) { //texts field type
					foreach ((array)$f['texts'] as $key => $f) {
						$this->parameters[$f['name']] = $this->get_value($f);
					}
				}
			}
		}
	}
}

// New
public function get_values() {
	foreach ( $this->tabs as $tab => $settings ) {
		foreach ( $settings['fields'] as $fields ) {
			foreach ( (array)$fields as $f ) {
				if ( isset( $settings['multiple'] ) )    // Changing the inner  $f['name']  with parent  $settings['multiple']
					$this->parameters[$f['name']] = $this->get_value($f);
				elseif($f['type'] == 'selects' && isset($f['selects'])) {
					foreach ($f['selects'] as $select) {
						$this->parameters[$select['name']] = $this->get_value($select);
					}
				}elseif($f['type'] == 'checkboxes' && isset($f['options'])) {
					foreach ((array)$f['options'] as $key => $value) {
						$this->parameters[$key] = $this->get_value(array('name' => $key));
					}
				}elseif($f['type'] == 'texts' && isset($f['texts'])) { //texts field type
					foreach ((array)$f['texts'] as $key => $f) {
						$this->parameters[$f['name']] = $this->get_value($f);
					}
				}
			}
		}
	}
}