Php function argument error suppression, empty() isset() emulation

Question

I\'m pretty sure the answer to this question is no, but in case there\'s some PHP guru

is it possible to write a function in a way where invalid arguments or non exi

Answer 1

If you simply add a default value to the parameter, you can skip it when calling the function. For example:

function empty($paramName = ""){
    if(isset($paramName){
        //Code here
    }
    else if(empty($paramName)){
        //Code here
    }
}

Answer 2

You don't get any error when a variable is passed by reference (PHP will create a new variable silently):

 function myHappyFunction(&$var)
 {       
 }

But I recommend against abusing this for hiding programming errors.

Answer 3

There are valid cases where checking becomes cumbersome and unnessesary.
Therfore i've written this little magic function:

/**
 * Shortcut for getting a value from a possibly unset variable.
 * Normal:
 *   if (isset($_GET['foo']) && $_GET['foo'] == 'bar') {
 * Short:
 *   if (value($_GET['foo']) == 'bar') {
 *
 * @param mixed  $variable 
 * @return mixed  Returns null if not set
 */
function value(&$variable) {
    if (isset($variable)) {
        return $variable;
    }
}

It doesn't require any changes to myHappyFunction().
You'll have to change

myHappyFunction($someBogusVar);

to

myHappyFunction(value($someBogusVar));

Stating your intent explicitly. which makes it good practice in my book.

Answer 4

@Sean That was already answered by Brian

return isset($input) ? $input : $default;

Answer 5

Sean, you could do:

$result = ($func_result = doLargeIntenseFunction()) ? $func_result : 'no result';

EDIT:

I'm sure there could be a great discussion on ternary operators vrs function calls. But the point of this question was to see if we can create a function that won't throw an error if a non existent value is passed in without using the '@'

And I told you, check it with isset(). A ternary conditional's first part doesn't check null or not null, it checks true or false. If you try to check true or false on a null value in PHP, you get these warnings. isset() checks whether a variable or expression returns a null value or not, and it returns a boolean, which can be evaluated by the first part of your ternary without any errors.

Answer 6

While the answer to the original question is "no", there is an options no one has mentioned.

When you use the @ sign, all PHP is doing is overriding the error_reporting level and temporarily setting it to zero. You can use "ini_restore('error_reporting');" to set it back to whatever it was before the @ was used.

This was useful to me in the situation where I wanted to write a convenience function to check and see if a variable was set, and had some other properties as well, otherwise, return a default value. But, sending an unset variable through caused a PHP notice, so I used the @ to suppress that, but then set error_reporting back to the original value inside the function.

Something like:

$var = @foo($bar);

function foo($test_var)
{
     ini_restore('error_reporting');

     if(is_set($test_var) && strlen($test_var))
     {
          return $test_var;
     }
     else
     {
          return -1;
     }
}

So, in the case above, if $bar is not set, I won't get an error when I call foo() with a non-existent variable. However, I will get an error from within the function where I mistakenly typed is_set instead of isset.

This could be a useful option covering what the original question was asking in spirit, if not in actual fact.