在PHP中，==與===的主要區(qū)別在于類型檢查的嚴格程度。==在比較前會進行類型轉(zhuǎn)換，例如5=="5"返回true，而===要求值和類型都相同才會返回true，例如5==="5"返回false。使用場景上，===更安全應(yīng)優(yōu)先使用，==僅在需要類型轉(zhuǎn)換時使用。

In PHP, the difference between == (loose comparison) and === (strict comparison) comes down to how strictly PHP checks for equality — especially when it comes to data types.

What does == do?

The double equals operator (==) compares values after type juggling, which means PHP will try to convert the types of the values to match before comparing them. This can sometimes lead to unexpected results if you're not careful.

Examples:

• 5 == "5" returns true because PHP converts the string "5" into an integer 5 before comparing.
• 1 == true returns true because both are considered truthy values, and true is treated as 1.
• "0" == false also returns true because "0" is treated like the boolean false.

So if you're only concerned about the value and not the type, == might seem convenient — but it can cause bugs that are hard to track.

How is === different?

The triple equals operator (===) checks both value and type. It won't do any type conversion. If two values are the same type and have the same value, then it returns true. Otherwise, it's false.

Examples:

• 5 === "5" returns false because one is an integer and the other is a string.
• 1 === true returns false since one is an integer and the other is a boolean.
• null === 0 returns false, even though both are falsy — again, because they’re different types.

This kind of strict comparison is usually safer in most situations, especially when working with functions or APIs that return specific types like false on failure.

When should you use each?

Use === by default unless you specifically need type coercion.

Here’s when == might be acceptable:

• When checking user input that may come in as strings but represent numbers.
• In cases where you expect either null or false and want to treat them similarly (but even this is risky).

But here's why you should prefer ===:

• Avoids surprises from automatic type conversion
• Makes your code more predictable and easier to debug
• Helps catch bugs early, like mistyped variables or incorrect return values

A common gotcha: many PHP functions return false on failure. If you check with ==, something like 0 or an empty string could falsely match and break your logic.

So unless you're certain you want type coercion, stick with ===.

基本上就這些。

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