How to check if post has Video or Gallery block in Gutenberg blocks?

One can use the built-in has_block( $block_type, $post ) function to check for specific blocks.

The first input argument is the block type in <!-- wp:{$block_type} --> and the second one is the post object.

To find the corresponding block type, we can view it in the Code Editor view via the shortcut:

Ctrl + Shift + Alt + M

or via the settings:

For example the gallery block will show as:

Example: Within The Loop

Checking for wp:gallery and wp:video blocks, within the loop, the corresponding block types are gallery and video:

if ( has_block( 'video' ) && has_block( 'gallery' ) ) {
   // ...
}

Example: Outside The Loop

For a given post object, we can use the second input argument of has_block() to determince if the post contains the wp:gallery and wp:video blocks:

$mypost = get_post( 123 );

if ( has_block( 'video', $mypost ) && has_block( 'gallery', $mypost ) ) {
   // ...
}

Example: Custom Block Within The Loop

Checking the content for a custom block with namespace: <!-- wp:custom/block -->, it would be:

if ( has_block( 'custom/block' ) ) {
   // ...
}