Everything Else

<?php
add_hook('AffiliateActivation', 1, function($vars) {
    // Perform hook code here...
});

<?php
add_hook('AffiliateClickthru', 1, function($vars) {
    // Perform hook code here...
});

<?php

//Skip applying the commission for affiliate 2
add_hook('AffiliateCommission', 1, function($vars) {
    $return = [];

    if ($vars['affiliateId'] == 2) {
        $return['skipCommission'] = true;
    }
    return $return;
});


//Ensure commission is applied for affiliate 3
add_hook('AffiliateCommission', 1, function($vars) {
    $return = [];

    if ($vars['affiliateId'] == 3) {
        $return['payout'] = true;
    }
    return $return;
});

<?php

//Do not open a ticket for affiliate 2
add_hook('AffiliateWithdrawalRequest', 1, function($vars) {
    $return = [];
    if ($vars['affiliateId'] == 2) {
        $return['skipTicket'] = true;
    }

    return $return;
});

<?php
add_hook('AfterConfigOptionsUpgrade', 1, function($vars) {
    // Perform hook code here...
});

<?php
add_hook('CCUpdate', 1, function($vars) {
    // Perform hook code here...
});

<?php
add_hook('CalcAffiliateCommission', 1, function($vars) {
    // Perform hook code here...
});

<?php

add_hook('CustomFieldLoad', 1, function($vars) {
    return array('value' => 'overridden value',);
});

<?php

add_hook('CustomFieldSave', 1, function($vars) {
    return array('value' => 'overridden value',);
});

<?php

//Do not log emails for userid 2
add_hook('EmailPreLog', 1, function($vars) {
    $return = [];

    if ($vars['userid'] == 2) {
        $return['abortLogging'] = true;
    }

    return $return;
});

//Override the saved subject of the email for userid 3
add_hook('EmailPreLog', 1, function($vars) {
    $return = [];

    if ($vars['userid'] == 3) {
        $return['subject'] = 'This subject is overridden';
    }

    return $return;
});

<?php

add_hook('EmailPreSend', 1, function($vars) {
    $merge_fields = [];
    if (!array_key_exists('my_custom_var', $vars['mergefields'])) {
        $merge_fields['my_custom_var'] = "My Custom Var";
        $merge_fields['my_custom_var2'] = "My Custom Var2";
    }
    if ($vars['messagename'] == 'My Message Name' && $vars['relid'] == 2) {
        //Stop the email from sending a specific message and related id.
        $merge_fields['abortsend'] = true;
    }
    $merge_fields['attachments'] = [
        [
            'filename' => 'invoice.pdf',
            'data' => file_get_contents('path/to/file.pdf'),
        ],
    ];

    return $merge_fields;
});

<?php

//Output additional merge fields in the list when editing an email template
add_hook('EmailTplMergeFields', 1, function($vars) {
    $merge_fields = [];
    $merge_fields['my_custom_var'] = "My Custom Var";
    $merge_fields['my_custom_var2'] = "My Custom Var2";
    return $merge_fields;
});

<?php

//Return an exchange rate for the XBT currency
add_hook('FetchCurrencyExchangeRates', 1, function($vars) {
    //Code here to fetch the the current exchange rate relative to EUR

    //Return exchange rate relative to 1 EUR
    return ['XBT' => 927.121,];
});

<?php

add_hook('IntelligentSearch', 1, function ($vars) {
    /**
     * This is an example of array return for an Intelligent Search.
     * This format is supported in the blend WHMCS Admin Template.
     * Any template based on blend and updated to WHMCS 7.7+ is also supported.
     */
    $searchResults = array();

    // look for exact matches in client notes field
    $result = \WHMCS\Database\Capsule::table('tblclients')
        ->where('notes', $vars['searchTerm'])
        ->get();

    foreach ($result as $client) {
        $searchResults[] = [
            'title' => $client->firstname . ' ' . $client->lastname, // The title of the search result. This is required.
            'href' => 'clientssummary.php?userid=' . $client->id, // The destination url of the search result. This is required.
            'subTitle' => $client->email, // An optional subtitle for the search result.
            'icon' => 'fal fa-user', // A font-awesome icon for the search result. Defaults to 'fal fa-star' if not defined.
        ];
    }
    return $searchResults;
});

<?php
add_hook('LinkTracker', 1, function($vars) {
    // Perform hook code here...
});

<?php
add_hook('LogActivity', 1, function($vars) {
    // Perform hook code here...
});

<?php

add_hook('NotificationPreSend', 1, function($vars) {

    $eventType = $vars['eventType'];
    $eventName = $vars['eventName'];
    $rule = $vars['rule'];
    $hookParameters = $vars['hookParameters'];
    $notification = $vars['notification'];

    // Perform additional conditional logic and throw the AbortNotification
    // exception to prevent the notification from sending.
    if ($eventType == 'Invoice'
        && $eventName == 'created'
        && (isset($hookParameters['invoiceid'])
            && $hookParameters['invoiceid'] > 1000)
    ) {
        throw new \WHMCS\Notification\Exception\AbortNotification();
    }

    // If allowing the notification to continue, you can manipulate the $notification
    // object using the interface, WHMCS\Notification\Contracts\NotificationInterface.
    $notification->setTitle('Override notification title');
    $notification->setMessage('Override notification message body');

});

<?php
add_hook('PayMethodMigration', 1, function($vars) {
    // Perform hook code here...
});

<?php
add_hook('PreEmailSendReduceRecipients', 1, function($vars) {
    // Perform hook code here...
});

<?php
add_hook('PreUpgradeCheckout', 1, function($vars) {
    // Perform hook code here...
});

<?php

//Stop the Domain Purchase for this Premium Domain
add_hook('PremiumPriceOverride', 1, function($vars) {
    return ['noSale' => true,];
});

//Force the Client to Contact Support to Purchase Domain
add_hook('PremiumPriceOverride', 1, function($vars) {
    return ['contactUs' => true,];
});

//Override the Register and Renew Pricing & Skip Markup Application
add_hook('PremiumPriceOverride', 1, function($vars) {
    return [
        'register' => 150.00,
        'renew' => 200.00,
        'skipMarkup' => true,
    ];
});

<?php
add_hook('PremiumPriceRecalculationOverride', 1, function($vars) {
    // Perform hook code here...
});

<?php
/**
 * Hook for VatNumberVerification must return a verification constant from
 * \WHMCS\Billing\VAT\Verification\VerificationInterface:
 * * STATE_VERIFIED - if the VAT number is registered
 * * STATE_UNVERIFIED - if the VAT number is not registered
 * * STATE_UNKNOWN - if the hook cannot determine the registration state of the
 *   VAT number
 *
 * Multiple hooks may be registered. When a hook responds with STATE_VERIFIED or
 * STATE_UNVERIFIED, the response is treated as authoritative and final.
 * By final:
 *  * when there are multiple hooks are registered, the first authoritative answer
 *    will be yielded to the application, and remaining registered hooks will not
 *    be consulted, and no additional integrated services will be consulted.
 *
 * If neither STATE_VERIFIED nor STATE_UNVERIFIED is yielded after process all
 * registered hooks, STATE_UNKNOWN will be used by the system. When the system
 * uses STATE_UNKNOWN, other integrated services of the system will be polled in
 * an attempt to get an authoritative, final response of STATE_VERIFIED or
 * STATE_UNVERIFIED.
 *
 * Two examples:
 * 1) a hook that uses custom logic for Ireland and Germany and all other EU regions
 * 2) a hook that allows some hypothetical test mode to give results for test numbers
 *
 * While these two could be in one hook, registering both illustrates the pipeline
 * for the verification request.
 */

add_hook('VatNumberVerification', 1, function($vars) {
    /** @var \WHMCS\Billing\VAT\VatNumber $vatNumber */
    $vatNumber = $vars['vatNumber'];
    $isValid = null;

    if ($vatNumber->getPrefix() == 'IE') {
        // Handle Ireland VAT numbers with custom logic
        $number = $vatNumber->getNumber(); // Example: '091234567'

        // custom logic here
        $isValid = customIrelandVatCheck($number);
    } elseif ($vatNumber->getPrefix() == 'DE') {
        // Handle Germany VAT numbers with custom logic
        $isValid = customGermanyVatCheck($vatNumber->getNumber());
    } elseif ($vatNumber->isEU()) {
        // Handle Germany VAT numbers with custom logic
        $isValid = customEuVatCheck($vatNumber->getNumber());
    }

    if ($isValid === false) {
        return \WHMCS\Billing\VAT\Verification\VerificationInterface::STATE_UNVERIFIED;
    } elseif ($isValid === true) {
        return \WHMCS\Billing\VAT\Verification\VerificationInterface::STATE_VERIFIED;
    } else {
        // let any other hook or the system give a final answer
        return \WHMCS\Billing\VAT\Verification\VerificationInterface::STATE_UNKNOWN;
    }
});

add_hook('VatNumberVerification', 1, function($vars) {
    /** @var \WHMCS\Billing\VAT\VatNumber $vatNumber */
    $vatNumber = $vars['vatNumber'];

    if ($someTestModeFlag) {
        if ($vatNumber->getIdentifier() == 'GB123456789') {
            return \WHMCS\Billing\VAT\Verification\VerificationInterface::STATE_VERIFIED;
        } elseif ($vatNumber->getIdentifier() == 'GB987654321') {
            return \WHMCS\Billing\VAT\Verification\VerificationInterface::STATE_UNVERIFIED;
        }
    }

    // let any other hook or the system give a final answer
    return \WHMCS\Billing\VAT\Verification\VerificationInterface::STATE_UNKNOWN;
});