explanation.md

get_file_data() Plugin example

Problem

You need to know the version of your plugin in your code. How do you do that? Maybe a constant, maybe a hard-coded string somewhere. Whichever way you go, you have at least 2 places where the plugin version lives: your hard-coded string/constant/whatever, and the plugin header used by WordPress. Updating things in more than one place is a pain.

Solution

Use the get_file_data() function to retrieve information about your plugin. Then use that in your code instead of hard-coding the value. BAM, only one place to update the version.

Why not use get_plugin_data() instead?

That function is only loaded inside the /wp-admin/ section of the dashboard, while get_file_data() is loaded everywhere.

file_data_sample.php

<?php
/**
 * Plugin Name: File Data Sample
 * Plugin URI: https://gist.github.com/JPry/49f26495b5f2a4a702bb
 * Version: 0.1.0
 * Description: A fun example of get_file_data() for a single location of a version.
 * Author: JPry
 */
 
class JPry_File_Data_Plugin {
	
	/**
	 * The transient key.
	 *
	 * @var string
	 */
	protected $transient_key = 'jpry_file_data_plugin_version';
	
	/**
	 * The plugin version.
	 *
	 * @var string
	 */
	protected $version = '';
	
	/**
	 * Constructor.
	 */
	public function __construct() {
		$this->setup_version();
	}
	
	/**
	 * Get the plugin version.
	 *
	 * @return string The plugin version.
	 */
	public function get_version() {
		return $this->version;
	}
	
	/**
	 * Retrieve the file version info from a transient.
	 *
	 * We store it in a transient because file reads can be heavy. This way we keep those to a minimum.
	 */
	private function setup_version() {
		$version = get_transient( $this->transient_key );
		
		// Set up the version if the transient is missing.
		if ( false === $version ) {
			// These are the headers you care about looking up.
			$headers = array(
				'version' => 'Version',
			);
			
			// Grab the data
			$data    = get_file_data( __FILE__, $headers );
			$version = $data['version'];
			
			// Store the transient for a week
			set_transient( $this->transient_key, $version, WEEK_IN_SECONDS );
		}

		$this->version = $version;
	}
}

$instance = new JPry_File_Data_Plugin();

// This will echo "0.1.0"
echo $instance->get_version();