fill_alt_tags

/*
 * Add Missing Alt Tags To WordPress Images : advanced
 * source : https://www.mwordpress.net/repair-alternative-alt-text-for-wordpress-images/
 * Mwordpress.net - مجلة ووردبريس
*/
function fill_alt_tags($content){
	
	global $post;
	preg_match_all('/<img (.*?)\/>/', $content, $images);
	
	$site_name = get_bloginfo('name');
	
	$char_array = array();
	$char_array[] = '-';
	$char_array[] = '_';
	
	if(!is_null($images)) {
		foreach($images[1] as $index => $value) {
			
			preg_match( '/src\s*=\s*([\'"])?((?(1).+?|[^\s>]+))(?(1)\1)/', $value, $source );
			
			// ALT tag : Not Found
			if(!preg_match('/alt=/', $value)) :
				$file = preg_replace( '/\-*(\d+)x(\d+)\.(.*)$/', ' ', $source[2] );
				$filename = pathinfo($file, PATHINFO_FILENAME);
				$text = str_replace( '/\-*(\d+)x(\d+)\.(.*)$/', ' ', $filename );
				$title = str_replace( $char_array, ' ', $text );
				$new_img = str_replace('<img', '<img alt="'.$title.' - '.$site_name.'"', $images[0][$index]);
				$content = str_replace($images[0][$index], $new_img, $content);
			endif;
			
			// ALT tag : Empty
			if(preg_match('/alt=/', $value) and strpos($value, 'alt=""')) :
				$file = preg_replace( '/\-*(\d+)x(\d+)\.(.*)$/', ' ', $source[2] ); 
				$filename = pathinfo($file, PATHINFO_FILENAME);
				$text = str_replace( '/\-*(\d+)x(\d+)\.(.*)$/', ' ', $filename );
				$title = str_replace( $char_array, ' ', $text );
				$new_img = str_replace('alt=""', 'alt="'.$title.' - '.$site_name.'"', $images[0][$index]);
				$content = str_replace($images[0][$index], $new_img, $content);
			endif;

		}
		return $content;
	}
	
}
add_filter('the_content', 'fill_alt_tags');