How do I read values (PHP defined constants) from wp-config.php?

Question

I need to get username, password etc from the wp-config file to connect to a custom PDO database.

Currently I have another file where I have this info, but

Answer 1

Here is a function to read all WP DB defines:

function get_wordpress_data() {
    $content = @file_get_contents( '../wp-config.php' );

    if( ! $content ) {
        return false;
    }

    $params = [
        'db_name' => "/define.+?'DB_NAME'.+?'(.*?)'.+/",
        'db_user' => "/define.+?'DB_USER'.+?'(.*?)'.+/",
        'db_password' => "/define.+?'DB_PASSWORD'.+?'(.*?)'.+/",
        'db_host' => "/define.+?'DB_HOST'.+?'(.*?)'.+/",
        'table_prefix' => "/\\\$table_prefix.+?'(.+?)'.+/",
    ];

    $return = [];

    foreach( $params as $key => $value ) {

        $found = preg_match_all( $value, $content, $result );

        if( $found ) {
            $return[ $key ] = $result[ 1 ][ 0 ];
        } else {
            $return[ $key ] = false;
        }

    }

    return $return;
}

this returns an array like this:

array (size=5)
  'db_name' => string '.........'
  'db_user' => string '.........'
  'db_password' => string '.........'
  'db_host' => string 'localhost'
  'table_prefix' => string 'wp_'