用于检查数组中的变量是否已设置的自定义函数

Question

What I'm trying to do is write one function to reuse vs writing out an if statement every time.

If statement:

if (!isset($value)){ echo 'null';}else{ echo $value;}

Function:

function isSetTest($value){
    if ( !isset($value)){
       $value = NULL;
    }
    return $value;
}

echo'name'.isSetTest($value);

Function works but I still get the "undefined" error message which is what i'm trying to avoid.

Answer 1

Pass by reference instead, so that no processing of the variable is done until you want it:

function isSetTest(&$value) { // note the &
    if (!isset($value)) {
       $value = NULL;
    }
    return $value;
}

You can shorten this a bit:

function isSetTest(&$value) {
    return isset($value) ? $value : null;
}

I have a function that does something similar, except you can provide an optional default value in the case that the variable is not set:

function isset_or(&$value, $default = null) {
    return isset($value) ? $value : $default;
}