PHP 8的match表達(dá)式通過嚴(yán)格比較提供更簡潔的條件映射。1. 使用嚴(yán)格相等（===）避免類型轉(zhuǎn)換；2. 無需break語句防止意外貫穿；3. 直接返回值可賦給變量；4. 支持多條件合并共享結(jié)果。適用于精確匹配、映射輸入輸出場景，如HTTP狀態(tài)碼處理；不適用于范圍檢查或需要松散比較的情況。

Match expressions in PHP 8 are a more concise and readable way to compare values and return a result based on the first matching condition. They’re similar to switch statements but offer cleaner syntax and stricter comparison behavior.

How match expressions work

A match expression compares a value against multiple conditions using strict equality (===) and returns a corresponding result. Unlike switch, you don’t need to write break; statements, and it’s designed to be an expression that returns a value.

Here's a basic example:

$status = 200;

$message = match($status) {
    200 => 'OK',
    404 => 'Not Found',
    500 => 'Internal Server Error',
    default => 'Unknown Status',
};

This makes code shorter and easier to read, especially when dealing with simple conditional mappings.

Key differences from switch

• Strict comparison: match uses ===, while switch uses == (loose comparison).
• No fall-through: You don’t have to worry about missing break; like in switch.
• Returns a value: You can assign the result of a match directly to a variable.

When to use match instead of switch

Use match when:

• You're comparing a single value against multiple exact matches.
• You want clean, compact code without break; or verbose syntax.
• You're mapping input values to output values (like HTTP status codes to messages).

Avoid match if:

• You need range checks (e.g., $x > 10).
• You're comparing loosely (e.g., '42' == 42).
• You rely on fall-through behavior intentionally.

In those cases, switch is still more flexible.

Multiple conditions per case

You can group multiple matching conditions together by separating them with commas. This is useful when different inputs should return the same result.

Example:

$role = 'editor';

$accessLevel = match($role) {
    'admin' => 10,
    'editor', 'contributor' => 5,
    'subscriber' => 1,
    default => 0,
};

This keeps your logic clear and avoids repeating the same return value for similar cases.

These expressions aren't meant to replace every switch statement, but they make a lot of common scenarios simpler and less error-prone. Once you start using them, especially for things like routing, status handling, or role-based access, you'll probably find yourself reaching for them often.

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