HOOK

• Filters
  • Add
  • Apply
  • Remove
• Action
  • Add
  • Do
  • Remove

Filters

This concept is based on Wordpress hook functions.

Reference: https://thachpham.com/wordpress/wordpress-development/cach-dung-filter-hook-trong-wordpress.html

Reference: https://viblo.asia/p/action-hook-va-filter-hook-trong-wordpress-p2-3P0lPyD45ox

#Add Filter

Reference: https://developer.wordpress.org/reference/functions/add_filter

function add_filter(string $tag, callable $function_to_add, int $priority = 10, int $accepted_args = 1)

#Description

Skilldo offers filter hooks to allow plugins to modify various types of internal data at runtime.

A plugin can modify data by binding a callback to a filter hook. When the filter is later applied, each bound callback is run in order of priority, and given the opportunity to modify a value by returning a new value.

The following example shows how a callback function is bound to a filter hook.

Note that $example is passed to the callback, (maybe) modified, then returned:

function example_callback( $example ) {
    // Maybe modify $example in some way.
    return $example;
}
add_filter( 'example_filter', 'example_callback' );

Bound callbacks can accept from none to the total number of arguments passed as parameters in the corresponding apply_filters() call.

In other words, if an apply_filters() call passes four total arguments, callbacks bound to it can accept none (the same as 1) of the arguments or up to four. The important part is that the $accepted_args value must reflect the number of arguments the bound callback actually opted to accept. If no arguments were accepted by the callback that is considered to be the same as accepting 1 argument. For example:

// Filter call.
$value = apply_filters( 'hook', $value, $arg2, $arg3 );

// Accepting zero/one arguments.
function example_callback() {
    ...
    return 'some value';
}
add_filter( 'hook', 'example_callback' ); // Where $priority is default 10, $accepted_args is default 1.

// Accepting two arguments (three possible).
function example_callback( $value, $arg2 ) {
    ...
    return $maybe_modified_value;
}
add_filter( 'hook', 'example_callback', 10, 2 ); // Where $priority is 10, $accepted_args is 2.

#Parameters

Parameter	Value	Description
tag	string (Required)	The name of the filter to hook the $function_to_add callback to.
function_to_add	callable (Required)	The callback to be run when the filter is applied.
priority	int | Default value: 10	Used to specify the order in which the functions associated with a particular action are executed. Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the action.
accepted_args	int | Default value: 1	The number of arguments the function accepts.

#Apply Filters

Reference: https://developer.wordpress.org/reference/functions/apply_filters

function apply_filters(string $tag, mixed $value)

#Description

The callback functions attached to filter hook $tag are invoked by calling this function. This function can be used to create a new filter hook by simply calling this function with the name of the new hook specified using the $tag parameter.

The function allows for additional arguments to be added and passed to hooks.

// Our filter callback function
function example_callback( $string, $arg1, $arg2 ) {
    // (maybe) modify $string
    return $string;
}
add_filter( 'example_filter', 'example_callback', 10, 3 );

/*
 * Apply the filters by calling the 'example_callback' function we
 * "hooked" to 'example_filter' using the add_filter() function above.
 * - 'example_filter' is the filter hook $tag
 * - 'filter me' is the value being filtered
 * - $arg1 and $arg2 are the additional arguments passed to the callback.*/
$value = apply_filters( 'example_filter', 'filter me', $arg1, $arg2 );

#Parameters

Parameter	Value	Description
tag	string (Required)	The name of the filter hook.
value	mixed (Required)	The value on which the filters hooked to $tag are applied on..

#Remove Filters

Reference: https://developer.wordpress.org/reference/functions/remove_filter

function remove_filter( string $tag, callable $function_to_remove, int $priority = 10 )

#Description

This function removes a function attached to a specified filter hook. This method can be used to remove default functions attached to a specific filter hook and possibly replace them with a substitute.

To remove a hook, the $function_to_remove and $priority arguments must match when the hook was added. This goes for both filters and actions. No warning will be given on removal failure.

#Parameters

Parameter	Value	Description
tag	string (Required)	The filter hook to which the function to be removed is hooked.
function_to_remove	callable (Required)	The name of the function which should be removed.
priority	int | Default value: 10	The priority of the function.

Actions

This concept is based on Wordpress hook functions.

Reference: https://thachpham.com/wordpress/wordpress-development/cach-su-dung-action-hook-trong-wordpress.html

Reference: https://viblo.asia/p/action-hook-va-filter-hook-trong-wordpress-p1-QpmleQqrlrd

#Add action

Reference: https://developer.wordpress.org/reference/functions/add_action

function add_action(string $tag, callable $function_to_add, int $priority = 10, int $accepted_args = 1)

#Description

Actions are the hooks that the core launches at specific points during execution, or when specific events occur.

Plugins can specify that one or more of its PHP functions are executed at these points, using the Action API.

#Parameters

Parameter	Value	Description
tag	string (Required)	The name of the filter to hook the $function_to_add callback to.
function_to_add	callable (Required)	The callback to be run when the filter is applied.
priority	int | Default value: 10	Used to specify the order in which the functions associated with a particular action are executed. Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the action.
accepted_args	int | Default value: 1	The number of arguments the function accepts.

#Do action

Reference: https://developer.wordpress.org/reference/functions/do_action

function do_action(string $tag, mixed $value)

#Description

This function invokes all functions attached to action hook $tag. It is possible to create new action hooks by simply calling this function, specifying the name of the new hook using the $tag parameter.

You can pass extra arguments to the hooks, much like you can with apply_filters().

#Parameters

Parameter	Value	Description
tag	string (Required)	The name of the filter hook.
value	mixed (Required)	The value on which the filters hooked to $tag are applied on..

#Remove action

Reference: https://developer.wordpress.org/reference/functions/remove_action

function remove_action( string $tag, callable $function_to_remove, int $priority = 10 )

#Description

This function removes a function attached to a specified filter hook. This method can be used to remove default functions attached to a specific filter hook and possibly replace them with a substitute.

To remove a hook, the $function_to_remove and $priority arguments must match when the hook was added. This goes for both filters and actions. No warning will be given on removal failure.

#Parameters

Parameter	Value	Description
tag	string (Required)	The filter hook to which the function to be removed is hooked.
function_to_remove	callable (Required)	The name of the function which should be removed.
priority	int | Default value: 10	The priority of the function.