PHP 动态字符串更新参考 [英] PHP dynamic string update with reference

问题描述

有没有办法做到这一点:

Is there any way to do this:

$myVar = 2;
$str = "I'm number:".$myVar;
$myVar = 3;

echo $str;

输出将是:"I'm number: 3";

我想要一个字符串，它的一部分就像一个指针，它的值将通过对引用变量的最后一次修改来设置.

I'd like to have a string where part of it would be like a pointer and its value would be set by the last modification to the referenced variable.

例如，即使我这样做:

 $myStr = "hi";
 $myStrReference = &$myStr;
 $dynamicStr = "bye ".$myStrReference;
 $myStr = "bye";
 echo $dynamicStr;

这将输出bye hi"，但由于最后一次更改，我希望它是bye bye".我认为问题在于将指针连接到字符串时，指针的值是所使用的值.因此，无法使用连接后设置的值输出字符串.

This will output "bye hi" but I'd like it to be "bye bye" due to the last change. I think the issue is when concatenating a pointer to a string the the pointer's value is the one used. As such, It's not possible to output the string using the value set after the concatenation.

有什么想法吗?

更新:$dynamicStr 将被附加到 $biggerString 和最后 $finalResult($biggerString+$dynamicStr) 将回显给用户.因此，我唯一的选择是做某种 echo eval($finalResult) 其中 $finalResult 里面会有一个 echo($dynamicStr)和 $dynamicStr='$myStr'(按照 Lawson 的建议)，对吗?

Update: the $dynamicStr will be appended to a $biggerString and at the end the $finalResult ($biggerString+$dynamicStr) will be echo to the user. Thus, my only option would be doing some kind of echo eval($finalResult) where $finalResult would have an echo($dynamicStr) inside and $dynamicStr='$myStr' (as suggested by Lawson), right?

更新:

$myVar = 2;
$str = function() use (&$myVar) {
    return "I'm number $myVar";
};

$finalStr = "hi ".$str();
$myVar = 3;
echo $finalStr; 

我希望它输出:我是 3 号"而不是我是 2 号"......但事实并非如此.

I'd like for this to ouput: "hi I'm number 3" instead of "hi I'm number 2"...but it doesn't.

推荐答案

这里的问题是，一旦一个变量被赋值(在你的例子中是一个字符串)，它的值在再次修改之前不会改变.

The problem here is that once a variable gets assigned a value (a string in your case), its value doesn't change until it's modified again.

>

你可以使用匿名函数来完成类似的事情:

You could use an anonymous function to accomplish something similar:

$myVar = 2;
$str = function() use (&$myVar) {
    return "I'm number $myVar";
};

echo $str(); // I'm number 2
$myVar = 3;
echo $str(); // I'm number 3

当函数被分配给 $str 时，它会保持变量 $myVar 从内部访问.在任何时间点调用它都会使用 $myVar 的最新值.

When the function gets assigned to $str it keeps the variable $myVar accessible from within. Calling it at any point in time will use the most recent value of $myVar.

更新

关于你的最后一个问题，如果你想进一步扩展字符串，你可以创建另一个包装器:

Regarding your last question, if you want to expand the string even more, you can create yet another wrapper:

$myVar = 2;
$str = function() use (&$myVar) {
    return "I'm number $myVar";
};

$finalStr = function($str) {
    return "hi " . $str();
}

$myVar = 3;

echo $finalStr($str);

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