Laravel 9 Blade用@标签报Undefined variable $__env错误求助

问题原因 #

你在Blade模板里用原生PHP定义了buildCategory递归函数，而Blade的指令（比如@foreach、@isset）依赖Laravel视图编译时的$__env环境变量才能正常工作。这个自定义函数处于原生PHP的独立作用域中，内部无法自动访问到Blade的$__env变量，所以使用Blade指令就会触发「Undefined variable $__env」错误；而原生PHP的foreach不依赖这个环境变量，因此能正常运行。

解决办法 #

方案1：使用视图组件重构递归逻辑（推荐） #

将分类树的递归生成逻辑移到Laravel视图组件中，脱离原生PHP函数的作用域限制，更符合Laravel的开发规范：

1. 创建组件类 app/View/Components/CategoryTree.php：

namespace App\View\Components;

use Illuminate\View\Component;

class CategoryTree extends Component
{
    public $category;

    public function __construct($category)
    {
        $this->category = $category;
    }

    public function render()
    {
        return view('components.category-tree');
    }

    public function buildCategory($parent)
    {
        if (!isset($this->category['parent_cats'][$parent])) {
            return '';
        }

        $html = '<ul>';
        foreach ($this->category['parent_cats'][$parent] as $cat_id) {
            foreach ($this->category['userPagePerms'] as $userPagePerm) {
                $selected = $userPagePerm->backend_page_permission_id == $cat_id ? 'true' : 'false';
                $cat = $this->category['categories'][$cat_id];
                
                if (!isset($this->category['parent_cats'][$cat_id])) {
                    $html .= "<li data-jstree='{\"selected\":{$selected},\"opened\":true}'>
                        <a href='{$cat->id}'>{$cat->name}</a>
                    </li>";
                } else {
                    $html .= "<li data-jstree='{\"selected\":{$selected},\"opened\":true}'>
                        <a href='{$cat->id}'>{$cat->name}</a>
                        {$this->buildCategory($cat_id)}
                    </li>";
                }
            }
        }
        $html .= '</ul>';
        return $html;
    }
}

2. 创建组件视图 resources/views/components/category-tree.blade.php：

{!! $component->buildCategory(0) !!}

3. 在原模板中调用组件：

<x-category-tree :category="$category" />

方案2：手动传递$__env变量到自定义函数 #

如果不想重构代码，可以在定义函数时手动传入$__env，让函数内部能访问Blade环境：

<?php function buildCategory($parent, $category, $__env){ ?>
@isset($category['parent_cats'][$parent])
    <ul>
        @foreach ($category['parent_cats'][$parent] as $cat_id)
            @foreach ($category['userPagePerms'] as $userPagePerm)
                @if (!isset($category['parent_cats'][$cat_id]))
                    <li data-jstree='{&quot;selected&quot;:{{ ($userPagePerm->backend_page_permission_id == $cat_id) ? 'true' : 'false' }},&quot;opened&quot;:true}'>
                        <a href='{{$category['categories'][$cat_id]->id }}'> {{ $category['categories'][$cat_id]->name}}</a>
                    </li>
                @endif
                @if (isset($category['parent_cats'][$cat_id]))
                    <li data-jstree='{&quot;selected&quot;:{{ ($userPagePerm->backend_page_permission_id == $cat_id) ? 'true' : 'false' }},&quot;opened&quot;:true}'>
                        <a href='{{ $category['categories'][$cat_id]->id }}'>{{$category['categories'][$cat_id]->name }}</a>
                            <?php buildCategory($cat_id, $category, $__env); ?>
                    </li>
                @endif
            @endforeach
        @endforeach
    </ul>
@endisset
<?php } buildCategory(0, $category, $__env); ?>

⚠️ 此方法仅作临时修复，不符合Laravel最佳实践，不推荐长期使用。

方案3：完全使用原生PHP实现递归 #

将所有Blade指令替换为原生PHP代码，彻底避开对$__env的依赖：

<?php function buildCategory($parent, $category){ 
    if(isset($category['parent_cats'][$parent])){ ?>
    <ul>
        <?php foreach ($category['parent_cats'][$parent] as $cat_id) {
            foreach ($category['userPagePerms'] as $userPagePerm) { ?>
                <?php if (!isset($category['parent_cats'][$cat_id])) { ?>
                    <li data-jstree='{"selected":<?php echo ($userPagePerm->backend_page_permission_id == $cat_id) ? 'true' : 'false'; ?>,"opened":true}'>
                        <a href='<?php echo $category['categories'][$cat_id]->id; ?>'> <?php echo $category['categories'][$cat_id]->name; ?></a>
                    </li>
                <?php } ?>
                <?php if (isset($category['parent_cats'][$cat_id])) { ?>
                    <li data-jstree='{"selected":<?php echo ($userPagePerm->backend_page_permission_id == $cat_id) ? 'true' : 'false'; ?>,"opened":true}'>
                        <a href='<?php echo $category['categories'][$cat_id]->id; ?>'><?php echo $category['categories'][$cat_id]->name; ?></a>
                            <?php buildCategory($cat_id, $category); ?>
                    </li>
                <?php } ?>
            <?php }
        } ?>
    </ul>
<?php }
} buildCategory(0, $category); ?>

内容的提问来源于stack exchange，提问作者Mustafa Bayram