if语句的可变范围问题（PHP） [英] Variable Scope issue with if statements ( PHP)

问题描述

好吧我似乎对PHP的变量范围存在误解，原谅我缺乏主题，因为我来自Java，C＃背景。认为我可以通过将函数放在函数外部来使函数或if语句可以访问变量。以下是我要完成的内容：

Alright I seem to have a misconception with variable scope with PHP, forgive my lack of the subject as I come from a Java, C# background. Thinking I could make variables accessible to functions or if statements simply by placing it outside it. Below is a snippet of what I'm trying to accomplish:

foreach ($nm as $row=>$im) {
    $itm_name = $im;
    $lnk = $lnk_cty[$row];  
    if($mode == 'addMenu') {
        $m = $m_id; //id will be coming from fresh insert of menu_name 
    } else {
        $m = $_POST['mnu_add'][$row];
        echo "MENU_ID: ".$m;
    }
    if($mode == 'addCat') {
        $m = $c_id; //id will be coming from fresh insert of cat_name
    } else {
 $m = $_POST['cat_add'][$row];
    }
    //used for testing purposes
    echo "item name: ".$itm_name ."<br />";
    echo "lnk: ".$lnk ."<br />";
    echo "m: ".$m ."<br />"; //$m is empty here, because its a new declaration as oppose to accessing $m value from if statement
    $display_fields .= "<li>".$itm_name." ".$item."</li>";
    $sql_array[] = '("' . $itm_name . '", "' . $lnk . '",  ' . $m . ')';  // Add a new entry to the queue 
}

现在我正在尝试do是使 $ m 变量值在if语句之外可以访问 $ m 变量 $ sql_array [] 声明。在C＃中，我只是在foreach循环之外声明一个变量并且能够使用它。在对此事进行一些阅读后，我发现使用全局或GLOBALS关键字只有在我的全局范围变量在foreach之前分配值并声明 global $ m 时才能使用在循环中获取该值。但是我的当前代码 $ m 属于if语句中的本地范围，并且每个人都不鼓励使用它们。现在，是否有更好的方法使 $ sql_array [] 语句可以访问 $ m ？

Now what I'm trying to do is make the $m variable values accessible outside the if statements its in to the $m variable used in the $sql_array[] statement. In C# I would simply declare a variable outside the foreach loop and be able to use it. After doing some reading on the matter I found that using the global or GLOBALS keywords would only work if my global scope variable is assign the value before the foreach, and declaring global $m to obtain that value within the loop. But with my current code $m is of a local scope within the if statements and everyone discourages using them. Now, is there a better method of making $m accessible to the $sql_array[] statement?

推荐答案

如果语句块没有自己的范围。无论您分配给 $ m 的数据是什么，都必须为空。尝试调试诸如 $ _ POST 变量之类的内容。此外， $ m_id 在哪里被定义？也许它也是空的。

If statement blocks do not have their own scope. Whatever data you are assigning to $m must be empty to begin with. Try debugging things like your $_POST variables. Also, where is $m_id being defined? Maybe it is empty as well.

PHP 确实在函数，类方法等中有范围。但如果语句没有自己的范围。例如，以下代码将回显您好！：

PHP does have scope inside functions, class methods and the like. But if statements do not have their own scope. For example, the following code would echo Hi there!:

$bool = true;
if ($bool) {
    $new_var = 'Hi there!';
}
echo $new_var;

读一下手册。

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