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How to pre-fill form field values

There are two ways to pre-fill form field values: via the values form arg (best for static data known at render time) or via the af/field/prefill_value filter (best when the value needs to be computed or conditional).

Pre-filling via the `values` form arg

When rendering the form with advanced_form(), pass a values array keyed by field name:

advanced_form( 'YOUR_FORM_KEY_HERE', [
    'values' => [
        'first_name' => 'John',
        'last_name'  => 'Doe',
    ],
] );

The values arg works with the function only — the [advanced_form ...] shortcode doesn’t currently support it.

Pre-filling via `af/field/prefill_value`

For programmatic / conditional pre-fills, hook the filter:

add_filter( 'af/field/prefill_value', function ( $value, $field, $form, $args ) {

    // Only run for the target form.
    if ( $form['key'] !== 'YOUR_FORM_KEY_HERE' ) {
        return $value;
    }

    if ( $field['name'] === 'first_name' ) {
        return 'John';
    }

    if ( $field['name'] === 'last_name' ) {
        return 'Doe';
    }

    return $value;

}, 10, 4 );

The filter fires per-field on render, so you can pull values from anywhere — wp_get_current_user(), a related post, an API call, the URL — and return them per $field['name'] (or $field['key'] if you prefer keys).

See also