PHP - array_implode

<?php
 /**
  * @purpose              : Joins an array containing any number of
  *                         sub-arrays based on the parameters sent
  *                         after $array
  * @param   array $array : The array to be joined.  This variable must
  *                         be an array, or a "Fatal, catchable error"
  *                         will be triggered
  * @param   mixed *      : Any parameters sent after $array will be
  *                         used to join $array.  It must be formatted
  *                         as either a string or an array; if an array
  *                         is sent, *[0] will used between elements,
  *                         *[1] will be placed before each element, and
  *                         *[2] will be placed after each element.  If
  *                         any of these values are omitted, their
  *                         respective defaults will be used.  If the
  *                         number of nested arrays is greater than the
  *                         number of extra arguments sent, a default
  *                         will be used.
  * @note                 : If too few arguments are sent, array_join
  *                         will attempt to use the constant
  *                         ARRAY_IMPLODE_DEFAULT_DELIM if it is set;
  *                         otherwise, an empty string is used.
  */
 function array_implode(array $array) {
    $argv=func_get_args();
    // Default joining deliminator
    $def_delim=defined("ARRAY_IMPLODE_DEFAULT_DELIM")
               ?ARRAY_IMPLODE_DEFAULT_DELIM
               :"";
    // Get this joining's deliminator
    $delim=isset($argv[1])
           ?$argv[1]
           :$def_delim;
    // Fix the value of $delim
    if (!is_array($delim)) {
       $delim=array(0=>"$delim");
    } elseif (!isset($delim[0])) {
       $delim[0]=$def_delim;
    }
    foreach (array(1,2) as $ind) {
       if (!isset($delim[$ind])) {
          $delim[$ind]="";
       }
    }
    // Save other deliminators for recursive calls
    $delims=array();
    foreach (array_slice($argv,2,count($argv),true) as $i => $d) {
       $delims[]="\$argv[$i]";
    }
    $delims=implode(",",$delims);
    $delims=$delims==""?"":",$delims";
    $strs=array();
    foreach ($array as $val) {
       $str=is_array($val)?eval("return array_implode(\$val$delims);"):$val;
       $strs[]=$delim[1].$str.$delim[2];
    }
    return implode($delim[0],$strs);
 }
?>

<?php
 header("Content-type: text/plain");
 $array=array(1,2,array(3,4,5),array(array(6,7),8),9);
 print_r($array);
 echo "\n".array_implode($array,array(" ","[","]"),"-");
 define("ARRAY_IMPLODE_DEFAULT_DELIM","_");
 echo "\n".array_implode($array,array(" ","[","]"),"-");
?>

Array
(
    [0] => 1
    [1] => 2
    [2] => Array
        (
            [0] => 3
            [1] => 4
            [2] => 5
        )

    [3] => Array
        (
            [0] => Array
                (
                    [0] => 6
                    [1] => 7
                )

            [1] => 8
        )

    [4] => 9
)

[1] [2] [3-4-5] [67-8] [9]
[1] [2] [3-4-5] [6_7-8] [9]