Is file_get_contents() the only way for plugins reading local files OR does WP_Filesystem_Direct::get_contents() even work?

Question

Background

I'm developing a plugin for WordPress. I initially used file_get_contents() for two purposes:

1. A remote file (which I changed to wp_remote_post())
2. A local file in the plugin dir (what this question is about)

WordPress staff told me to NOT use file_get_contents() for remote _POST requests (usage 1. above), but to use wp_remost_post() instead.

From their email concerning usage 1. (above):

Using file_get_contents on remote files

Many hosts block the use of file_get_contents on remote content. This is a security measure that we fully endorse.

Thankfully, WordPress comes with an extensive HTTP API that can be used instead. It’s fast and more extensive than most home-grown alternatives. It’ll fall back to curl if it has to, but it’ll use a lot of WordPress’ native functionality first.

So, I did. But...

Solving usage 1. A remote file (above) got me to reading and thinking about a better tool for usage 2. A local file (above)

In the WordPress HTTP API docs, there is no alternative for file_get_contents() on local files, nothing like wp_file_get_contents().

(I understand this may seem strange since local files of a plugin are often static, but I am writing extra files to save cost, and I politely don't want to open that discussion. Besides, this approved plugin from someone else, code here, uses file_get_contents(), thus proving my own need is legitimate, but it doesn't prove that file_get_contents() is 'proper' WordPress-practice.)

From this blog post, clearly this was a big discussion for file_get_contents() for remote files. But, I don't see much on the web about a WordPress function for local files. From the post:

Like many others I’ve used the native PHP function file_get_contents() to receive the content from a remote file because the functions is very easy to use. But is it the best way to do that? I see many scripts using that function and even WordPress plugins are using this function while WordPress has a native function to receive remote content.

...I want to take that discussion to local files and build this plugin right.

My code (current and attempted)

I simply need to confirm whether a local file in the plugin directory exists, then confirm whether it contains a certain string. I thought it best to use file_get_contents() for local files in PHP from this question on SE. But, this is WordPress. Currently, I am using:

if ( ( ! $wp_filesystem->exists ( $check_this_file ) )
 || (strpos ( file_get_contents ( $check_this_file ),
    $check_this_string ) === false ) )

I tried using WP_Filesystem_Direct::get_contents instead:

if ( ( ! $wp_filesystem->exists ( $check_this_file ) )
 || (strpos ( WP_Filesystem_Direct::get_contents ( $check_this_file ),
    $check_this_string ) === false ) )

...but I got this error:

Deprecated: Non-static method WP_Filesystem_Direct::get_contents() should not be called statically

What should I do?

I'm not sure because there isn't even a #get-contents tag on WP.SE at the time of asking, but the function exists both in the framework and in the docs.

I want to know the "WordPress way" for plugins to read a plugin file's contents for a string test:

• file_get_contents() (what I have now)
• WP_Filesystem_Direct::get_contents() (but how do I make it work without the error?)
• or some proper-reliable usage of wp_filesystem() or similar

Answer 1

The alternate of using file_get_contents() is to initiate WP_Filesystem and use its $wp_filesystem->get_contents method.

Here is a clean example method on how to use it

Example

<?php
     /**
     * This method gets a list of the most popular Google web fonts. 
     * Initialize the WP filesystem and no more using file_put_contents function
     *
     * @see     wp_filesystem()
     * @see     get_parent_theme_file_path()
     * @return  array   A list of Google web fonts
     */
    function mm_get_google_fonts() {
 
    // Call globals
    global $wp_filesystem;

    // You have to require following file in the front-end only. In the back-end; its already included
    require_once ( ABSPATH . '/wp-admin/includes/file.php' );

    // Initiate
    WP_Filesystem();
     
    $local_file =   get_parent_theme_file_path( '/assets/json/google-web-fonts.json' );
    $content    =   '';
 
    if ( $wp_filesystem->exists( $local_file ) ) {

        // following is alternate to
        // $content = json_decode( file_get_contents( $local_file ) );

        $content = json_decode( $wp_filesystem->get_contents( $local_file ) );

    } // End If Statement
 
    return $content;
 
} 
?>

For more information you can visit the official documenation of WP_Filesystem

Answer 2

$wp_filesystem->get_contents is wrong for this purpose, since you can't know what filesystem path the file is going to be accessible at using WP_Filesystem . If the user has WP_Filesystem using chrooted FTP or SFTP to the WP install dir, the server path /path/to/site/wp will need to actually be /site/wp in order for WP_Filesystem to find the file. But if you're not chrooted, it's at /path/to/site/wp

To reliably read your file you need to instantiate WP_Filesystem_Direct and then use that.

$wpfsd = new WP_Filesystem_Direct( false );
$wpfsd->get_contents ( $check_this_file )

Answer 3

$wp_filesystem->get_contents()

$wp_filesystem->get_contents() replaced file_get_contents() perfectly as a drop-in replacement. Of course, it must be initiated with WP_Filesystem(); first.

Here is a before and after example...

Before:

if ( (strpos ( file_get_contents ( $check_this_file ),
    $check_this_string ) === false) ) {...}

After:

WP_Filesystem();
if ( (strpos ( $wp_filesystem->get_contents ( $check_this_file ),
    $check_this_string ) === false) ) {...}