composerでmPDFをインストールする

php composer.phar require mpdf/mpdf

vendor/cakephp-plugins.php

return [
    'plugins' => [
        'Bake' => $baseDir . '/vendor/cakephp/bake/',
        'BootstrapUI' => $baseDir . '/vendor/friendsofcake/bootstrap-ui/',
        'DebugKit' => $baseDir . '/vendor/cakephp/debug_kit/',
        'Migrations' => $baseDir . '/vendor/cakephp/migrations/',
        'WyriHaximus/TwigView' => $baseDir . '/vendor/wyrihaximus/twig-view/',
        'Mpdf' => $baseDir . '/vendor/mpdf/mpdf/',  // 追加
    ],
];

bootstrap.php

\App\Application::addPlugin('Mpdf');  // 追加

ソースコード

$mpdf = new Mpdf();
$mpdf->WriteHTML('
Hello world!
');
$mpdf->Output();

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