Highend Theme - Featured image with custom ALT attribute.

custom-functions.php

function highend_featured_image_thumb( $args = array() ) {

    $args = wp_parse_args(
        $args,
        array(
            'post_id'  => '',
            'width'    => false,
            'height'   => false,
            'crop'     => false,
            'alt'      => '',
            'lightbox' => false,
        )
    );

    $post_id = $args['post_id'];

    $thumb = get_post_thumbnail_id( $post_id );
    $image = highend_resize( $thumb, $args['width'], $args['height'], $args['crop'] );

    // If custom ALT tag is provided use it, otherwise use page title.
    if ( empty( $args['alt'] ) ) {
        $thumb_alt = trim( strip_tags( get_post_meta( $thumb, '_wp_attachment_image_alt', true ) ) ); // phpcs:ignore

        if ( ! empty( $thumb_alt ) ) {
            $args['alt'] = $thumb_alt;
        } else {
            $args['alt'] = get_the_title();
        }
    }

    if ( empty( $image ) || ! isset( $image['url'] ) || empty( $image['url'] ) ) {
        return; 
    }

    if ( $args['lightbox'] ) {
        $atts = 'data-title="' . esc_attr( get_the_title( $post_id ) ) . '" href="' . esc_url( wp_get_attachment_url( $thumb ) ) . '" rel="prettyPhoto"';
    } else {
        $atts = 'href="' . esc_url( get_permalink( $post_id ) ) . '"';
    }

    $srcset = $args['crop'] ? '' : ' srcset="' . esc_attr( wp_get_attachment_image_srcset( $thumb, array( $image['width'], $image['height'] ) ) ) . '"';

    ?>
    <div class="featured-image item-has-overlay">
        <a <?php echo $atts; ?>>
            <img src="<?php echo esc_url( $image['url'] ); ?>" alt="<?php echo esc_attr( $args['alt'] ); ?>" width="<?php echo esc_attr( $image['width'] ); ?>" height="<?php echo esc_attr( $image['height'] ); ?>"<?php echo $srcset; ?> />
            <div class="item-overlay-text">
                <div class="item-overlay-text-wrap">
                    <span class="plus-sign"></span>
                </div>
            </div>
        </a>
    </div>
    <?php
}