How to: Get the first image from the post and display it

First, paste this function on your functions.php file.

function catch_that_image() {
  global $post, $posts;
  $first_img = '';
  ob_start();
  ob_end_clean();
  $output = preg_match_all('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i', $post->post_content, $matches);
  $first_img = $matches [1] [0];

  if(empty($first_img)){ //Defines a default image
    $first_img = "/images/default.jpg";
  }
  return $first_img;
}



Once done, you can simply call the function within the loop to display the first image from the post:
<?php echo catch_that_image() ?>