Disable Heading 1

Earlier I have used this in functions.php:

// Customize the format dropdown items
if( !function_exists('base_custom_mce_format') ){
	function base_custom_mce_format($init) {
		// Add block format elements you want to show in dropdown
		$init['theme_advanced_blockformats'] = 'p,h2,h3';
		// Add elements not included in standard tinyMCE dropdown p,h1,h2,h3,h4,h5,h6
		//$init['extended_valid_elements'] = 'code[*]';
		return $init;
	}
	add_filter('tiny_mce_before_init', 'base_custom_mce_format' );
}

What can I do now to disable heading 1?

Right, the options in the TinyMCE config have changed: https://www.tinymce.com/wiki.php/Configuration. I believe you’re looking for this: https://www.tinymce.com/wiki.php/Configuration:block_formats.

Thank for an answet.

Can you give me a hint were to place this piece of code?
I tried this in functions.php, but it’s not working at all:

function myformatTinyMCE($in)
{
 $in['entity_encoding']= 'block_formats: "Paragraph=p;Header 2=h2;Header 3=h3"'; // numeric/raw
 return $in;
}
add_filter('tiny_mce_before_init', 'myformatTinyMCE' );

That’s not the right code (copy/paste error?). Perhaps try:

function myformatTinyMCE($in) {
  $in['block_formats'] = "Paragraph=p;Header 2=h2;Header 3=h3";
  return $in;
}
add_filter('tiny_mce_before_init', 'myformatTinyMCE' );

Thanks Andrew, it worked perfectly! :)) Wow!