What PHP function will print the name of an array with its contents?

Question

When I use Smart::Comments in Perl, I can see the name of the hash I am dumping (i.e. %person, below). . .

[pdurbin@macbook ~]$ cat /tmp/person.pl
#!/usr/bin/perl
use strict;
use warnings;
use Smart::Comments;
my %person = (
    'hair' => 'golden',
    'eyes' => 'blue',
);
### %person
[pdurbin@macbook ~]$ perl /tmp/person.pl

### %person: {
###            eyes => 'blue',
###            hair => 'golden'
###          }
[pdurbin@macbook ~]$

. . . but in PHP I only see "Array", no mention of $person. . .

[pdurbin@macbook ~]$ cat /tmp/person.php 
<?php
$person = array(
    'hair' => 'golden',
    'eyes' => 'blue',
);
print_r($person);
[pdurbin@macbook ~]$ php /tmp/person.php
Array
(
    [hair] => golden
    [eyes] => blue
)
[pdurbin@macbook ~]$

I've tried print_r(), var_export(), and var_dump() but is there some other PHP function that will print the name of an array with its contents?

Answer 1

A variable name in PHP is just a reference to the actual array. There can be multiple variables that refer to the same array. So it's not possible to find the name of an array.

Answer 2

You will have to print the name of the variable separately, unfortunately. You could wrap this in your own function to make it easier:

function print_r_WithName($varName,$return=FALSE){
  $retVal='';
  if(!$return){
    print "$varName:";
  }
  else{
    $retVal=$varName.':';
  }

  $retval.=print_r($$varName,$return);

  return $retVal
}

and then call it as

print_r_WithName("person");

//output:
person:Array
(
  [hair] => golden
  [eyes] => blue
)

Answer 3

As JW pointed out already, PHP (like JavaScript as I have just recently found out) passes the data inside the array to be accessed by the var_dump, it does not pass that reference name. As the language is structured there's not really a way for it to know the name without passing a reference to that function. The data inside is aware of how many references there are to it, but it has no way of knowing which one you want, (including any prototyping and constructing that goes on behind the scenes during parsing).

However, here is a GODAWFUL HACK that I have used (under duress) to get that information.

function AwesomeDump($data, $reference=null)
   {
   $myreturn = "";
   if ($reference) { $myreturn = $reference;}
   $myreturn .= var_dump($data);
   return $myreturn;
   }

In this case to execute it, you'll need to provide the reference name as the second argument to specify WHICH name you want it to have. It defaults to null so it works just my var_dump unless you specify otherwise.

Answer 4

You can't, there is no such thing as this Smart::Comments in PHP.

If you want to track variable values, then you should use a debugger, like xdebug

Answer 5

Actually, it is possible, but in an extremely hackish way. You can use debug_backtrace() to get the number of the line (and the filename, of course) where the running function was called from. This allows you to parse that line to find out the expression (e.g. $myArray) which was evaluated (e.g. to array(1, 2, 3)) and passed to the running function. However, it is not easy to find out where the expression starts and ends without using complicated solutions like Tokenizer.

Presuming that the getArgumentExpressionAsString() is already implemented, the "dumping" function would look like this:

function dump($arg)
{
    $backtrace = debug_backtrace();
    $expression = getArgumentExpressionAsString($backtrace[0]);
    echo "$expression:";
    var_dump($arg);
}

EDIT. An example implementation:

function getArgumentExpressionAsString($backtrace)
{
    $allLines = file($backtrace['file']);
    $line =  $allLines[$backtrace['line'] - 1];
    $function = $backtrace['function'];
    return preg_replace("/.*{$function}\((.*)\).*/", '$1', $line);
}

function dump($arg)
{
    $backtrace = debug_backtrace();
    $expression = getArgumentExpressionAsString($backtrace[0]);
    echo "$expression:\r\n";
    var_dump($arg);
}

$arr = array(1, 2, 3);

dump($arr);

The output would be:

$arr:array(3) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
}