在Laravel的Blade模板引擎中，@if用於條件邏輯，@foreach用於循環(huán)遍歷數(shù)組或集合。 1.使用@if時，基本語法為@if($condition)顯示內容@endif，並支持@else與@elseif實現(xiàn)多條件判斷；2.使用@foreach時，通過@foreach($items as $item)循環(huán)輸出內容，並推薦配合@endforelse或@forelse處理空數(shù)據(jù)情況；3.其他常見指令包括@unless（相反條件）、@isset（檢查變量是否存在）、@empty（檢查變量是否為空）、@switch/@case（多條件匹配）、@auth/@guest（用戶認證狀態(tài)判斷）；4.注意事項包括確保變量已定義、避免在視圖中修改數(shù)據(jù)、正確關閉指令及清除緩存以提升性能。

In Laravel's Blade templating engine, directives like @if , @foreach , and others are used to write clean conditional logic and loops inside your views. You don't need to write raw PHP — Blade handles it in a more readable way.

How to Use @if for Conditional Logic

Blade's @if directive works just like a regular PHP if statement but with cleaner syntax inside HTML templates.

Basic usage looks like this:

 @if($condition)
    <!-- Show something when true -->
@endif

You can also add @else or @elseif :

 @if($score > 90)
    <p>Excellent!</p>
@elseif($score > 60)
    <p>You passed.</p>
@else
    <p>Try again.</p>
@endif

This is especially useful for showing different content blocks depending on user roles, data availability, or form validation results.

A common mistake is forgetting that variables must be defined in the controller or view composer. If $score isn't passed from the controller, you'll get an error.

Looping with @foreach (and What to Watch For)

The @foreach directive helps you loop through arrays or collections. It's most often used to display lists of items, such as blog posts or products.

Here's how it works:

 @foreach($items as $item)
    <div>{{ $item->name }}</div>
@endforeach

If there's a chance the list could be empty, use @forelse instead:

 @forelse($items as $item)
    <div>{{ $item->name }}</div>
@empty
    <p>No items found.</p>
@endforelse

• Make sure $items is not null before looping.
• Avoid modifying data directly in the view — keep logic in controllers.
• You can access the loop index via $loop->index , $loop->iteration , etc.

Some developers forget to check whether the variable is set or is actually an array/collection, which can cause errors.

Other Commonly Used Blade Directives

Besides @if and @foreach , here are a few other handy directives:

• @unless : Opposite of @if . Runs when the condition is false.

   @unless(Auth::check())
      Please log in.
  @endunless

• @isset : Checks if a variable is declared and not null.

• @empty : Checks if a variable is empty (null, empty string, empty array, etc).

• @switch / @case : Useful when handling multiple conditions on the same value.

• @auth / @guest : Shorthand for checking user authentication status.

These directives help reduce inline PHP and make templates easier to read and maintain.

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A Few Tips for Working With Blade Directives

• Always close your directives properly ( @endif , @endforeach , etc).
• Don't overdo logic in views — keep complex logic in controllers or services.
• Use comments like {{-- This is a Blade comment --}} for internal notes.
• Blade caches compiled views by default — run php artisan view:clear after major template changes.

基本上就這些。

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