Question

How Can I get the string that present the variable in function argument?

example

function dbg($param){
      return "param"; 

 }
 $var="Hello World";
 echo dgb($var);

output: var

 $arr=array();
 echo dgb($arr);

output: arr

Answer 1

It is NOT possible to do what you ask reliably.

The closest you can come up to doing that is to do a debug_backtrace() to check which file called the function then tokenize the source of that file to find the reference.

Again, this will not work reliably. It will fail if you have multiple calls on one line. Truthfully, it isn’t work the trouble. You are writing the code anyway, you know which variable you are passing.

function dbg($var) {
  $bt = debug_backtrace();
  $file = $bt[0]['file'];
  $line = $bt[0]['line'];

  $source = file_get_contents($file);

  $tmpTokens = token_get_all($source);
  $tokens = array ();

  foreach ($tmpTokens as $token) {
    if (is_array($token) && $token[0] !== T_INLINE_HTML && $token[0] !== T_WHITESPACE) {
      $tokens[] = $token;
    }
  }

  unset($tmpTokens);

  $countTokens = count($tokens);

  for ($i = 0; $i < $countTokens; $i++) {
    if ($tokens[$i][3] > $line || $i === $countTokens - 1) {
      $x = $i - (($tokens[$i][3] > $line) ? 1 : 0);

      for ($x; $x >= 0; $x--) {
        if ($tokens[$x][0] === T_STRING && $tokens[$x][1] === __FUNCTION__) {
          if ($x !== $countTokens - 1 && $tokens[$x + 1][0] === T_VARIABLE) {
            return $tokens[$x + 1][1];
          }
        }
      }
    }
  }

  return null;
}