auto-link-dashicons.php

<?php

function get_hr_link_type($link_url) {

	//strip query string (everything after the ?)
	$link_url = preg_replace('/\?.*/', '', $link_url);

	// get the file extension
	$pathinfo = pathinfo($link_url);
	$filetype = $pathinfo['extension'];

	$document_extensions = array('pdf','jpg','jpeg','gif','tif','png','pptx','pptm','ppt','pot','potx','potm','wav','mp3','mp4','avi','flv','mov','mpg','rm','swf','wmv','zip','xls','xla','xlb','xlc','xld','xlk','xll','xlm','xlt','xlv','xlw','doc','docx');

	$in_array = in_array($filetype, $document_extensions);

	if( empty($filetype) || $in_array == FALSE ){
		$reg_exUrl = "/(http|https|ftp|ftps)\:\/\/[a-zA-Z0-9\-\.]+\.[a-zA-Z]{2,3}(\/\S*)?/";
		if(preg_match($reg_exUrl, $link_url, $url)) {
			$filetype = 'web';
		} else {
			$filetype = 'unknown';
		}
	}


	switch ($filetype)
	{
		case "web":
			$icon_type = 'web';
			break;
		case "pdf":
			$icon_type = 'pdf';
			break;
		case "jpg":
		case "png":
		case "gif":
		case "jpeg":
		case "tif":
			$icon_type = 'image';
			break;
		case "pptx":
		case "pptm":
		case "ppt":
		case "pot":
		case "potx":
		case "potm":
			$icon_type = 'presentation';
			break;
		case "wav":
		case "mp3":
			$icon_type = 'audio';
			break;
		case "mp4":
		case "avi":
		case "flv":
		case "mov":
		case "mpg":
		case "rm":
		case "swf":
		case "wmv":
			$icon_type = 'video';
			break;
		case "zip":
			$icon_type = 'zip';
			break;
		case "xls":
		case "xla":
		case "xlb":
		case "xlc":
		case "xld":
		case "xlk":
		case "xll":
		case "xlm":
		case "xlt":
		case "xlv":
		case "xlw":
			$icon_type = 'spreadsheet';
			break;
		case "doc":
			$icon_type = 'word-doc';
			break;
		case "docx":
			$icon_type = 'open-doc';
			break;
		case "unknown":
			$icon_type = 'default';
			break;
		default:
			$icon_type = 'default';
	}



	return $icon_type;
}


function get_link_dashicon($link_url) {
	$link_type = get_link_type($link_url);

	switch ($link_type)
	{
		case "web":
			$icon = 'dashicons-admin-links';
			break;
		case "pdf":
			$icon = 'dashicons-media-document';
			break;
		case "jpg":
		case "png":
		case "gif":
		case "jpeg":
		case "tif":
			$icon = 'dashicons-format-image';
			break;
		case "pptx":
		case "pptm":
		case "ppt":
		case "pot":
		case "potx":
		case "potm":
			$icon = 'dashicons-media-interactive';
			break;
		case "wav":
		case "mp3":
			$icon = 'dashicons-controls-volumeon';
			break;
		case "mp4":
		case "avi":
		case "flv":
		case "mov":
		case "mpg":
		case "rm":
		case "swf":
		case "wmv":
			$icon = 'dashicons-format-video';
			break;
		case "zip":
			$icon = 'dashicons-media-archive';
			break;
		case "xls":
		case "xla":
		case "xlb":
		case "xlc":
		case "xld":
		case "xlk":
		case "xll":
		case "xlm":
		case "xlt":
		case "xlv":
		case "xlw":
			$icon = 'dashicons-media-spreadsheet';
			break;
		case "doc":
			$icon = 'dashicons-media-text';
			break;
		case "docx":
			$icon = 'dashicons-media-text';
			break;
		default:
			$icon = 'dashicons-admin-links';
	}

	return $icon;

}

function the_hr_link_dashicon($link_url) {
  echo get_hr_link_dashicon($link_url);
}

scripts.php

// Load stylesheets, and load dashicons as a dependency

function hr_load_your_css(){
	if(!is_admin()){
		$css_link = get_stylesheet_directory_uri() . '/assets/css/style.min.css';
		$css_file = get_stylesheet_directory() . '/assets/css/style.min.css';
		wp_enqueue_style('theme-style', $css_link, array('dashicons'), filemtime($css_file), 'all');
	}
}
add_action('wp_enqueue_scripts', 'hr_load_your_css');

usage.php

<a href="<?php echo esc_url( $resource_link ); ?>"><i class="dashicons <?php the_hr_link_dashicon($resource_link); ?>"></i> View document</a>