Change excerpt length of first post

Question

I have created a custom excerpt length in my functions.php, I would like to extend this function to increase the excerpt length of the first post in a loop.

My function at the moment:

/* Change Excerpt length */
function custom_excerpt_length( $length ) {
    return 30;
}

Was thinking of something along these lines

function new_excerpt_length($length) {
    global $post;
    if ($post-> FIRST POST?)
        return 50;
    else
        return 20;
}

Is there a way of getting post count from $post->?

Answer 1

Use the current_post property of the WP_Query object:

function new_excerpt_length($length) {
    global $wp_query; // assuming you are using the main query
    if ( 0 === $wp_query->current_post)
        return 50;
    else
        return 20;
}

The function may need further tweaks to avoid interfering with other queries in unintended ways, but that is the basic idea.

Answer 2

Another approach:

function custom_excerpt_length( $length ) 
{
    static $instance = 0;
    return ( in_the_loop() && 0 == $instance++ ) ? 50 : 20;
}

where we use simple counting inside the loop.