在PHP中，默認(rèn)情況下函數(shù)傳遞變量是通過值傳遞的，這意味著函數(shù)接收到的是原始變量值的一個副本。 1. 當(dāng)你將一個變量傳遞給函數(shù)時，函數(shù)內(nèi)部對該變量的修改不會影響到函數(shù)外部的原始變量；2. 如果希望在函數(shù)內(nèi)部修改原始變量，可以通過返回新值並在調(diào)用後重新賦值給原始變量來實現(xiàn)；3. 使用全局變量雖然可行，但通常不被推薦，因為它會使代碼難以維護和調(diào)試；4. PHP對大型數(shù)據(jù)結(jié)構(gòu)如數(shù)組或?qū)ο筮M(jìn)行了內(nèi)部優(yōu)化（如寫時復(fù)制），因此值傳遞的性能影響通常很小。因此，在使用值傳遞時，需注意上述特性以確保代碼正確性和效率。

In PHP, variables are passed by value to functions by default. That means when you pass a variable to a function, the function receives a copy of that variable's value, not a reference to the original variable. Any changes made inside the function won't affect the original variable outside.

Here's how it works and what you should know:

Understanding Pass-by-Value in PHP

When you call a function and give it a variable, PHP creates a new variable inside the function with the same value as the one you passed in. This is pass-by-value.

 function addOne($number) {
    $number = 1;
    echo "Inside function: $number\n";
}

$value = 5;
addOne($value);
echo "Outside function: $value\n";

Output:

 Inside function: 6
Outside function: 5

As you can see, even though $number was changed inside the function, the original $value outside stayed the same.

When You Might Want to Modify the Original

If you want to change the original variable from within a function, you might be tempted to try something like this:

 function modify($var) {
    $var = 'modified';
}

$original = 'original';
modify($original);
echo $original; // Still prints 'original'

But again, because PHP passes variables by value by default, this won't work unless you use references (which is a different topic).

So if your goal is to update the original variable, passing by value alone isn't enough.

Best Practices When Working With Value Passing

• Use return values wisely: If you need to update a value, return the new value from the function and assign it back.

   function addTax($price) {
      return $price * 1.1; // Adds 10% tax
  }
  
  $total = 100;
  $total = addTax($total); // Update the original value

• Avoid relying on global variables: While possible, using global or $GLOBALS is generally discouraged because it makes code harder to maintain and debug.

• Be aware of data types: For large data structures like arrays or objects, passing by value may seem inefficient, but PHP uses internal optimizations (like copy-on-write), so performance impact is usually minimal.

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Passing variables by value in PHP is straightforward — just pass them normally. The key takeaway is that any changes inside the function don't affect the original variable unless you explicitly return and reassign the value.基本上就這些。

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