Recently I was required to dump the source code of a closure in php, for debugging purposes. Here comes my first working approach. As it is just the first approach, I would really appreciate comments on what is not working for you, and what should be additionally possible. Here comes the code:

function closure_dump(Closure $c) {
    $str = 'function (';
    $r = new ReflectionFunction($c);
    $params = array();
    foreach($r->getParameters() as $p) {
        $s = '';
        if($p->isArray()) {
            $s .= 'array ';
        } else if($p->getClass()) {
            $s .= $p->getClass()->name . ' ';
        }
        if($p->isPassedByReference()){
            $s .= '&';
        }
        $s .= '$' . $p->name;
        if($p->isOptional()) {
            $s .= ' = ' . var_export($p->getDefaultValue(), TRUE);
        }
        $params []= $s;
    }
    $str .= implode(', ', $params);
    $str .= '){' . PHP_EOL;
    $lines = file($r->getFileName());
    for($l = $r->getStartLine(); $l < $r->getEndLine(); $l++) {
        $str .= $lines[$l];
    }
    return $str;
}

Imagine you have the following closure:

$f = function (Closure $a, &$b = -1, array $c = array())
  use ($foo) 
{
    echo $this->name;
    echo 'test';
};

Then closure_dump() will give you the following output:

function (Closure $a, &$b = -1, array $c = array (
)){
 use ($foo)
{
    echo $this->name;
    echo 'test';
};

As you can see, the debugging output is already nice, there are only problems with the formatting of the default value of the third, array, parameter. Maybe I’ll enhance this once. So far it should be at least useful for debugging.

Happy Coding!