Prepare WordPress post for Image LazyLoading by replacing the src Attribute

lazyload.php

<?php
/** 
 * Lozad
 * Attribute replacement refernce from: https://gist.github.com/ahmadassaf/9332846
 */
function faster_replace_img_src( $content ){
	if ( function_exists( 'is_amp_endpoint' ) && ! is_amp_endpoint() ) {
		$html = preg_replace_callback( '#(<img\s[^>]*src)="([^"]+)"#' , 'callback_img' , $content );
		$html = preg_replace( '/(<img\s[^>]*)class="(.*)"/', '$1 class="lozad $2"' , $html );
		$html = preg_replace( '/(<img\s[^>]*)srcset="(.*)"/', '$1 data-srcset="$2"' , $html );
	
		// $html = preg_replace( '/(<img\s[^>]*)class="(.*)"srcset="(.*)"/', '$1 class="lozad $2" data-srcset="$3"', $html );
		return $html;
	} else {
		return $content;
	}
}

function callback_img( $match ) {
	list( , $img, $src) = $match;
	return "$img=\"$preloading_image\" data-src=\"$src\" ";
}

add_filter( 'the_content', 'faster_replace_img_src' );