Functions (PHP) snippets

A Functions snippet holds plain PHP. Anything you would put in a theme’s functions.php or a small site-specific plugin belongs here: hooks, filters, helper functions, classes, integrations with other plugins.

Writing one

Write the code without an opening <?php tag. FluentSnippets writes that itself when it saves the file, and it refuses to save a snippet that starts with one, because a second tag would be printed onto the page as text.

add_action( 'init', function () {
    remove_post_type_support( 'post', 'comments' );
    remove_post_type_support( 'page', 'comments' );
} );

A closing ?> at the end is stripped for you, so you can leave one in if you paste code that has it.

Run locations

“Admin Only” is checked with is_admin(), so it also covers admin-ajax.php requests, which WordPress treats as admin requests. If that matters for your snippet, add your own wp_doing_ajax() check.

When your code runs

This is the one thing worth understanding properly, because it changes depending on a setting you might not connect to timing.

• Without conditional logic, a Functions snippet is attached to setup_theme. That is very early: before the theme’s functions.php is loaded, and before init.
• With conditional logic enabled, it is attached to wp instead. That is much later, after the main query has run, because the conditions need to know what page is being requested before they can be evaluated.

Why it matters: something like add_filter( 'template_include', … ) works fine in an unconditional snippet but is too late to have any effect if you enable conditional logic on the same snippet.

Within a hook, the Priority field controls ordering. See Priority.

Validation on save

PHP snippets are checked before the file is written. The check has two parts:

1. A parse pass over the code’s tokens, looking for syntax errors and for functions, classes or interfaces you are redeclaring.
2. A runtime pass that briefly evaluates the code to surface errors a parse cannot see.

If either fails, you get the error and nothing is saved. This is why a typo produces a message in the editor rather than a white screen on the front end.

The second pass means your code is executed once at save time. Keep that in mind for a snippet with side effects, such as one that writes a file or sends a request the moment it is loaded. Wrap that work in a hook rather than running it at the top level, which you want to be doing anyway.

Redeclaration errors

Because every published Functions snippet is loaded on the same request, two snippets that both define function my_helper() will fatal. The validator catches the obvious case at save time, but it cannot see a function defined by your theme or another plugin.

Prefix your function names, or guard them:

if ( ! function_exists( 'acme_price_suffix' ) ) {
    function acme_price_suffix( $price ) {
        return $price . ' inc. VAT';
    }
}

Things Functions snippets cannot do

• Print output directly. A Functions snippet runs long before the page is rendered, so echo at the top level either goes nowhere or lands somewhere unhelpful. Use a Content snippet for output.
• Run before plugins load. Snippets are attached from plugins_loaded, so you cannot use one to affect something that happens earlier in the WordPress boot. That belongs in wp-config.php or a must-use plugin.

Examples

Register a custom shortcode

add_shortcode( 'current_year', function () {
    return esc_html( gmdate( 'Y' ) );
} );

Remove the WordPress version from the head

remove_action( 'wp_head', 'wp_generator' );

Change the excerpt length

add_filter( 'excerpt_length', function () {
    return 30;
}, 999 );

Add a body class on a specific template

add_filter( 'body_class', function ( $classes ) {
    if ( is_page( 'pricing' ) ) {
        $classes[] = 'is-pricing';
    }
    return $classes;
} );