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  • Guide to Standardized Hooks - The describe() Method
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Introduction

The describe() method embeds hook action code attributes in your hook action code. This provides a programmatic means for the action code to express the developer's intended use of the hook. 

Basic usage

To use the describe() method, create a describe subroutine that returns the appropriate category, event, stage, and other attributes for the manage_hooks utility.

For more information, read our The manage_hooks Utility and Hook Action Code documentation.

The describe() method in Perl modules

In Perl modules, the describe() method must return a Perl array reference, which  must  contain one or more hash references. 

  • Each hash reference relates to one hookable action and creates a single entry for the Standardized Hooks database.
  • The hash reference must, at minimum, contain the categoryeventstageexectype, and hook descriptors.

The describe() method in scripts

Important:

Scripts must include argument evaluation in the hook action code in order to use the describe() method. When you register hooks with script hook action code, the manage_hooks utility calls the script with the --describe argument. 

In scripts, the describe() method must return a JSON-encoded string. When you decode the string, the JSON structure must be an array that contains one or more hashes, or associative arrays. 

  • Each hash reference relates to one hookable action and creates a single entry for the Standardized Hooks database.
  • The hash reference must, at minimum, contain the categoryeventstageexectype, and hook descriptors.

Make certain that the hook descriptor uses the correct method to invoke the script in order to perform the hookable action.

  • If the script is monolithic, and performs internal logic based on the context, provide the script's absolute path and filename.
  • If the script can parse input arguments via a shell argument array (for example, $argv or @argv), it should specify the absolute path and filename and the argument to switch to the proper code block.

Examples

The following examples contain describe method information and subroutines for two hooks:

  1. The first hook's information executes the add() subroutine (the MyApp::WHM::add() subroutine in the Perl module example) after cPanel & WHM creates an account. 
  2. The second hook's information executes the remove() subroutine (the MyApp::WHM::remove() subroutine in the Perl module example) prior to the account's deletion.

Note:

Click a tab to view the example for that type of hook action code. 

# Package this module.
package MyApp::WHM;
 
# Return errors if Perl experiences problems.
use strict;
use warnings; 
   
# Properly decode JSON.
use JSON;
 
# Embed hook attributes alongside the action code.
sub describe {
    my $my_add = {
        'category' => 'Whostmgr',
        'event'    => 'Accounts::Create',
        'stage'    => 'post',
        'hook'     => 'MyApp::WHM::add',
        'exectype' => 'module',
    };

    my $my_remove = {
        'blocking' => 1,
        'category' => 'Whostmgr',
        'event'    => 'Accounts::Remove',
        'stage'    => 'pre',
        'hook'     => 'MyApp::WHM::remove',
        'exectype' => 'module',
    };

    return [$my_add, $my_remove];
}

sub add {
    my ( $context, $data ) = @_;                 # Get the data that the system passes to the hook.

    my $result  = 0;                             # This boolean value is set to fail.     
    my $message = 'This is an error message.';   # This string is a reason for $result.
    
    # Insert your actions here.

    # Return the hook's result and message.
    return $result, $message;
}

sub remove {
    my ( $context, $data ) = @_;                 # Get the data that the system passes to the hook.

    my $result  = 0;                             # This boolean value is set to fail.     
    my $message = 'This is an error message.';   # This string is a reason for $result.
    
    # Insert your actions here.

    # Return the hook's result and message.
    return $result, $message;
}
 
1;
#!/usr/local/cpanel/3rdparty/bin/php -q
<?php
// file - /var/cpanel/myapp/whm.php 

// Any switches passed to this script 
$switches = (count($argv) > 1) ? $argv : array();

// Argument evaluation.
if (in_array('--describe', $switches)) {
    echo json_encode( describe() );
    exit;
} elseif (in_array('--add', $switches)) {
    list($status, $msg) = add();
    echo "$status $msg";
    exit;
} elseif (in_array('--remove', $switches)) {
    list($status, $msg) = remove();
    echo "$status $msg";
    exit;
} else {
    echo '0 myapp/whm.php needs a valid switch';
    exit(1);
}

// Embed hook attribute information.
function describe() {
    $my_add = array(
        'category' => 'Whostmgr',
        'event'    => 'Accounts::Create',
        'stage'    => 'post',
        'hook'     => '/var/cpanel/myapp/whm.php --add',
        'exectype' => 'script',
    );
    $my_remove = array(
        'blocking' => 1,
        'category' => 'Whostmgr',
        'event'    => 'Accounts::Remove',
        'stage'    => 'pre',
        'hook'     => '/var/cpanel/myapp/whm.php --remove',
        'exectype' => 'script',
    );
    return array($my_add, $my_remove);
}

function add() {
    // Your actions go here. 
}

function remove() {
    // Your actions go here. 
}
?>