Detailed explanation of how to use functions to add and perform actions in WordPress, detailed explanation of wordpress_PHP tutorial

Detailed explanation of how to use functions to add and execute actions in WordPress, detailed explanation of 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) The action name of the mounted function.

Default value: None

$function_to_add

(Callback function) (required) The function to be mounted, 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 value: 10

$accepted_args

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

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" content="width=device-width,initial-scale=1,maximum-scale=1,user-scalable=0" />';
}
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 generally exists in a special node. Or on events (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 perform.

$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 into the callback. The function operates based on the article id.

Return value

None

Example

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

Screen printing:

Test

For more reference, apply_filters(): http://www.endskin.com/apply_filters/

Others

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

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