是否可以在不获取“未定义变量”消息的情况下调用未定义的变量？

Question

I'm trying to make a simple little templating system where I don't want to define every variable that's available in the template. For example.

Every page would have

<?php displayHTML($variable); ?> 

but only some pages would actually have $variable defined.

$variable = "something";

In included functions.php I have tried

function displayHTML($variable){
if(isset($variable)){
echo $variable;
}else{
echo '';
        }
}

But the error seems to be coming from the fact that $variable isn't defined rather than not being set with a value. This error only shows with E_ALL enabled and I know I can shut it with @ or simply defining $variable across the board. Any function or best practice to avoid having to do this?

I know this seems weird but I would like to option to not define every variable if its not gonna be used on a page.

Answer 1

Define each variable before you use it.

If your templates are trying to use variables that don't exist, then that is a logical fault with your design, and you should fix that.

Give them some "default" or empty value if that's the visualisation that you wish to assign to those values.

Leaving them undefined is simply error-prone and, forgive me for saying so, lazy.

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Some people would tell you to use the @ error-suppressant. This is a fast, cheap, hacky workaround to an underlying fault... and my advice would be to steer well clear of it.