Detailed explanation of how to use functions to add and perform actions in WordPress

add_action() (add action) The
add_action() function is used to mount a function to the action hook.

Usage

add_action( $tag, $function_to_add, $priority, $accepted_args );

Parameters

$hook

(String) (Required) Action name of the mount function.

Default value: None

$function_to_add

(callback function) (required) For the mounted function, just fill in the function name in the form of a string.

Default value: None

$priority

(integer) (optional) The priority of action execution. The smaller the value, the first it will be executed.

Default: 10

$accepted_args

(integer) (optional) The callback function receives several arguments.

Default value: 1

Return value

(Boolean) Always returns True.

Example

Mount a function to the wp_head action and print something in the head tag.

function Bing_wp_head_test_print(){
  echo '<meta name="viewport" c />';
}
add_action( 'wp_head', 'Bing_wp_head_test_print' );

Others

This function is located at: wp-includes/plugin.php

do_action() (execute action)
do_action() is used to execute action hooks. The difference between it and apply_filters() is that there is no return value. It simply executes the function mounted by the plug-in or theme developer in a specific place, which usually exists on a special node or event (such as when starting to load the theme template or when publishing an article).

Usage

do_action( $tag, $arg... );

Parameters

$tag

(String) (Required) The name of the action to be performed.

$arg

(mixed) (optional) Additional parameters will be passed to the called function. Unlimited numbers can be added. For example, when the save_post action is triggered when saving an article, the id of the saved article can be inserted. , let the callback function operate based on the article id.

Return value

None

Example

function func(){
  echo '测试';
}
add_action( 'test', 'func' );
do_action( 'test' );

Screen print:

Test

More references similar apply_filters(): http://www.endskin.com/apply_filters/

Other

this The function is located at: wp-includes/plugin.php

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