如何将PHP函数的参数设置为默认值 [英] How to set a PHP function's param to a variable as the default value

问题描述

所以我希望能够根据变量是真还是假来开启或关闭某个功能。这个函数仍然会执行，但是因为这个变量是false，所以它不会做例程。

类似于这个

  $ testTF =T; 
 
函数Test（$ test = $ testTF）{
 echo $ test; 
} 
 
测试（Go）; 
  

当然，这不起作用，但我想知道是否有办法让它工作像打算一样。这个函数遍布在脚本中的任何地方，并且需要在某些地方，所以我不能将它们全部组合在一个if语句中，因为它会破坏它们。

我知道你可以在每次调用它时将值作为一个标志传递，但是我正在寻找一种方法来让它将该值作为默认值，除非另有说明。也许我正在寻找全局变量，但是我知道这很危险。

谢谢

解决方案

  $ testTF =T;您可以这样做吗？ 
 
函数Test（$ test = NULL）{
 if（$ test === NULL）{
 global $ testTF; 
 $ test = $ testTF; 
} 
 echo $ test; 
} 
 
测试（Go）; 
  

或者，如果您反对使用全局变量，则可以将默认值封装在函数中，如（$ test === NULL）{

  function Test（$ test = NULL）{
 if（$ test === NULL）{
 $ test = getDefault（）; 
} 
 echo $ test; 
} 
 
测试（Go）; 
 
函数getDefault（）{
 //从任何地方拉取默认值
 $ testDefault ='T'; 
 return $ testDefault; 
} 
  

So I'd like to be able to switch a certain function on or off depending on if a variable is true or false. The function would still execute, but because the variable is false, it won't do it's routine.

Something like this

$testTF = "T";

function Test($test=$testTF){
echo $test;
}

Test("Go");

Of course this won't work, but I'm wondering if there's a way to make it work like intended. This function is sprinkled everywhere in the script, and needs to be in certain places, so I can't just group them all together under one if statement because it would break them.

I know you could just pass the value as a flag every time you call it, but I'm looking for a way to make it assume that value as default unless told otherwise. Maybe I'm looking at globals here but that's dangerous I'm told.

Thanks

解决方案

Could you do this?

$testTF = "T";

function Test($test=NULL){
    if ($test ===NULL) {
        global $testTF;
        $test = $testTF;
    }
    echo $test;
}

Test("Go");

Optionally, if you're against using globals, you can encapsulate the default value in a function, like this:

function Test($test=NULL){
    if ($test ===NULL) {        
        $test = getDefault();
    }
    echo $test;
}

Test("Go");

function getDefault(){
    //pull default value from wherever
    $testDefault = 'T';
    return $testDefault;
}

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