Is there a way to get the name of a variable? PHP - Reflection

Question

I know this is not exactly reflection, but kind of. I want to make a debug function that gets a variable and prints a var_dump and the variable name.

Of course, when

Answer 1

I know I'm answering a 4 year old question but what the hell...

compact() might help you is your friend here!

I made a similar function to quickly dump out info on a few chosen variables into a log for debugging errors and it goes something like this:

function vlog() {
    $args = func_get_args();
    foreach ($args as $arg) {
        global ${$arg};
    }
    return json_encode(compact($args));
}

I found JSON to be the cleanest and most readable form for these dumps for my logs but you could also use something like print_r() or var_export().

This is how I use it:

$foo = 'Elvis';
$bar = 42;
$obj = new SomeFancyObject();

log('Something went wrong! vars='.vlog('foo', 'bar', 'obj'));

And this would print out like this to the logs:

Something went wrong! vars={"foo":"Elvis","bar":42,"obj":{"nestedProperty1":1, "nestedProperty2":"etc."}}

Word of warning though: This will only work for variables declared in the global scope (so not inside functions or classes. In there you need to evoke compact() directly so it has access to that scope, but that's not really that big of a deal since this vlog() is basically just a shortcut for json_encode(compact('foo', 'bar', 'obj')), saving me 16 keystrokes each time I need it.

Answer 2

Nope, not possible. Sorry.

Answer 3

You can do it by converting the variable to a key/value set before passing it to the function.

function varName($theVar) {  
   $variableName = key($theVar);  
   $variableValue = $theVar[$variableName];  
   echo ('The name of the variable used in the function call was '.$variableName.'<br />');  
   echo ('The value of the variable used in the function call was '.$variableValue.'<br />');  
}
$myVar = 'abc';
varName(compact('myVar'));

Though I don't recommend creating a reference to a nameless variable, function varName(&$theVar) works too.

Since compact() takes the variable name as a string rather than the actual variable, iterating over a list of variable names should be easy.

As to why you would want to do this -- don't ask me but it seems like a lot of people ask the question so here's my solution.

Answer 4

No, the closer you will get is with get_defined_vars().

EDIT: I was wrong, after reading the user comments on get_defined_vars() it's possible with a little hack:

function ev($variable){
    foreach($GLOBALS as $key => $value){
        if($variable===$value){
            echo '<p>$'.$key.' - '.$value.'</p>';
        }
    }
}

$lol = 123;

ev($lol); // $lol - 123

Only works for unique variable contents though.

Answer 5

I know this is very very late, but i did it in a different way.

It might honestly be a bit bad for performance, but since it's for debugging it shouldn't be a problem.

I read the file where the function is called, on the line it was called and I cut out the variable name.

function dump($str){
    // Get the caller with debug backtrace
    $bt = debug_backtrace();
    $caller = array_shift($bt);

    // Put the file where the function was called in an array, split by lines
    $readFileStr = file($caller['file']);

    // Read the specific line where the function was called
    $lineStr = $readFileStr[$caller['line'] -1];

    // Get the variable name (including $) by taking the string between '(' and ')'
    $regularOutput = preg_match('/\((.*?)\)/', $lineStr, $output);
    $variableName = $output[1];

    // echo the var name and in which file and line it was called
    echo "var: " . $variableName . " dumped in file: " . $caller['file'] . ' on line: ' . $caller['line'] . '<br>';

    // dump the given variable
    echo '<pre>' . var_export($str, true) . '</pre>';
}