insert php at within the_content

like to insert the following php below and left aligned wrapped at the start of the_content.

everywhere where the_content() is used?

possibly use a filter function; https://codex.www.ads-software.com/Plugin_API/Filter_Reference/the_content

code added to functions.php of your theme; example:

add_filter( 'the_content', 'info_before_the_content' );

function info_before_the_content( $text ) {
  global $post;

  $text = '<span class="alignleft pre-content-info">';
  $text .= get_the_post_thumbnail( $post->ID );
  if((get_post_meta($post->ID, "byline", true))) {
    $text .= '<p class="inside_byline">by ' . get_post_meta($post->ID, 'byline', true);
    $text .= '<span class="coltitle">' . get_post_meta($post->ID, 'column name', true) . '</span>';
    $text .= '</p>';
  }
  $text .= '</span>'; 

return $text;
}

use .pre-content-info { ... } for additional formatting.

(not tested)

alchymyth, thank you so much. Looks good. Will try it out. and will post again.

Thanks for you help on this I think Im getting progress.

Although some slight hitches:

1. I used your code and put in functions.php.
The thumbnail and other custom fields appeared as I wanted. Although the rest of the content did not appear.

2. And as an extra since you asked where I want the function to apply I was hoping it the function would happen only in specific categories.

Many thanks in advance.

1.
my mistake;

1. + 2.
try:

add_filter( 'the_content', 'info_before_the_content' );

function info_before_the_content( $text ) {
  global $post;

  if( is_single() && in_category( array('cat1','cat2','cat3') ) ) {
    $pretext = '<span class="alignleft pre-content-info">';
    $pretext .= get_the_post_thumbnail( $post->ID );
    if((get_post_meta($post->ID, "byline", true))) {
      $pretext .= '<p class="inside_byline">by ' . get_post_meta($post->ID, 'byline', true);
      $pretext .= '<span class="coltitle">' . get_post_meta($post->ID, 'column name', true) . '</span>';
      $pretext .= '</p>';
    }
    $pretext .= '</span>';
    $text = $pretext . $text;
  }
return $text;
}

https://codex.www.ads-software.com/Function_Reference/in_category

Perfect!!! You are awesome, alchymyth! Very helpful , patient and clear.