检查是否设置了作为参数传递的变量

Question

I want to check if a variable called $smth is blank (I mean empty space), and I also want to check if it is set using the function I defined below:

function is_blank($var){
    $var = trim($var);
    if( $var == '' ){
        return true;
    } else {
        return false;
    }
}

The problem is I can't find a way to check if variable $smth is set inside is_blank() function. The following code solves my problem but uses two functions:

if( !isset($smth) || is_blank($smth) ){
    // code;
}

If I use an undeclared variable as an argument for a function it says:

if( is_blank($smth) ){
    //code;
}

Undefined variable: smth in D:\Www\www\project\code.php on line 41

Do you have a solution for this?

Solution

This is what I came up with:

function is_blank(&$var){ 
    if( !isset($var) ){ 
        return true; 
    } else { 
        if( is_string($var) && trim($var) == '' ){ 
            return true; 
        } else { 
            return false; 
        } 
    } 
}

and works like a charm. Thank you very much for the idea, NikiC.

Answer 1

Simply pass by reference and then do isset check:

function is_blank(&$var){
    return !isset($var) || trim($var) == '';
}