Description:
------------
Massively nested arrays are decoded as null by json_decode.

Admittedly, an array this deep has its own concerns, but with no warnings or notices, documentation of the limit would be advisable.

The following code has 2 arrays, the first is 18 levels, the second is 19. The first decodes correctly, the second decodes as null.

Whilst an array MAY not be this deep, it is possible that objects containing objects with arrays COULD produce a depth of 19 levels. Sure, not exactly LEAN, but that's why this is just a minor doc issue and not a more important code issue.

The issue is with json_decode as json_encode quite happily encodes the larger array - an inconsistency maybe as the json_decode dox does say any json_encode'd output (though I am awaiting the changes due to bug#38680).

It also makes no difference if you use the 'assoc' option (json_decode's second paramater of True) to produce an associative array. The limit is still reached at 19 levels.

Reproduce code:
---------------
<?php
$a_array = 
	array('One' => array('Two' => array('Three' => array('Four' => 
	array('Five' => array('Six' => array('Seven' => array('Eight' => 
	array('Nine' => array('Ten' => array('Eleven' => array('Twelve' => 
	array('Thirteen' => array('Fourteen' => array('Fifteen' => 
	array('Sixteen' => array('Seventeen' => array('Eighteen' => 
	array(1,2,3)))))))))))))))))));
var_dump(json_encode($a_array));
var_dump(json_decode(json_encode($a_array)));

$a_array = 
	array('One' => array('Two' => array('Three' => array('Four' => 
	array('Five' => array('Six' => array('Seven' => array('Eight' => 
	array('Nine' => array('Ten' => array('Eleven' => array('Twelve' => 
	array('Thirteen' => array('Fourteen' => array('Fifteen' => 
	array('Sixteen' => array('Seventeen' => array('Eighteen' => 
	array('Nineteen' => array(1,2,3))))))))))))))))))));
var_dump(json_encode($a_array));
var_dump(json_decode(json_encode($a_array)));
?>

Expected result:
----------------
string(195) "{"One":{"Two":{"Three":{"Four":{"Five":{"Six":{"Seven":{"Eight":{"Nine":{"Ten":{"Eleven":{"Twelve":{"Thirteen":{"Fourteen":{"Fifteen":{"Sixteen":{"Seventeen":{"Eighteen":[1,2,3]}}}}}}}}}}}}}}}}}}"
object(stdClass)#1 (1) {
  ["One"]=>
  object(stdClass)#2 (1) {
    ["Two"]=>
    object(stdClass)#3 (1) {
      ["Three"]=>
      object(stdClass)#4 (1) {
        ["Four"]=>
        object(stdClass)#5 (1) {
          ["Five"]=>
          object(stdClass)#6 (1) {
            ["Six"]=>
            object(stdClass)#7 (1) {
              ["Seven"]=>
              object(stdClass)#8 (1) {
                ["Eight"]=>
                object(stdClass)#9 (1) {
                  ["Nine"]=>
                  object(stdClass)#10 (1) {
                    ["Ten"]=>
                    object(stdClass)#11 (1) {
                      ["Eleven"]=>
                      object(stdClass)#12 (1) {
                        ["Twelve"]=>
                        object(stdClass)#13 (1) {
                          ["Thirteen"]=>
                          object(stdClass)#14 (1) {
                            ["Fourteen"]=>
                            object(stdClass)#15 (1) {
                              ["Fifteen"]=>
                              object(stdClass)#16 (1) {
                                ["Sixteen"]=>
                                object(stdClass)#17 (1) {
                                  ["Seventeen"]=>
                                  object(stdClass)#18 (1) {
                                    ["Eighteen"]=>
                                    array(3) {
                                      [0]=>
                                      int(1)
                                      [1]=>
                                      int(2)
                                      [2]=>
                                      int(3)
                                    }
                                  }
                                }
                              }
                            }
                          }
                        }
                      }
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}
string(208) "{"One":{"Two":{"Three":{"Four":{"Five":{"Six":{"Seven":{"Eight":{"Nine":{"Ten":{"Eleven":{"Twelve":{"Thirteen":{"Fourteen":{"Fifteen":{"Sixteen":{"Seventeen":{"Eighteen":{"Nineteen":[1,2,3]}}}}}}}}}}}}}}}}}}}"
object(stdClass)#1 (1) {
  ["One"]=>
  object(stdClass)#2 (1) {
    ["Two"]=>
    object(stdClass)#3 (1) {
      ["Three"]=>
      object(stdClass)#4 (1) {
        ["Four"]=>
        object(stdClass)#5 (1) {
          ["Five"]=>
          object(stdClass)#6 (1) {
            ["Six"]=>
            object(stdClass)#7 (1) {
              ["Seven"]=>
              object(stdClass)#8 (1) {
                ["Eight"]=>
                object(stdClass)#9 (1) {
                  ["Nine"]=>
                  object(stdClass)#10 (1) {
                    ["Ten"]=>
                    object(stdClass)#11 (1) {
                      ["Eleven"]=>
                      object(stdClass)#12 (1) {
                        ["Twelve"]=>
                        object(stdClass)#13 (1) {
                          ["Thirteen"]=>
                          object(stdClass)#14 (1) {
                            ["Fourteen"]=>
                            object(stdClass)#15 (1) {
                              ["Fifteen"]=>
                              object(stdClass)#16 (1) {
                                ["Sixteen"]=>
                                object(stdClass)#17 (1) {
                                  ["Seventeen"]=>
                                  object(stdClass)#18 (1) {
                                    ["Eighteen"]=>
                                    object(stdClass)#19 (1) {
                                      ["Nineteen"] =>
                                        array(3) {
                                        [0]=>
                                        int(1)
                                        [1]=>
                                        int(2)
                                        [2]=>
                                        int(3)
                                      }
                                    }
                                  }
                                }
                              }
                            }
                          }
                        }
                      }
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}

Actual result:
--------------
string(195) "{"One":{"Two":{"Three":{"Four":{"Five":{"Six":{"Seven":{"Eight":{"Nine":{"Ten":{"Eleven":{"Twelve":{"Thirteen":{"Fourteen":{"Fifteen":{"Sixteen":{"Seventeen":{"Eighteen":[1,2,3]}}}}}}}}}}}}}}}}}}"
object(stdClass)#1 (1) {
  ["One"]=>
  object(stdClass)#2 (1) {
    ["Two"]=>
    object(stdClass)#3 (1) {
      ["Three"]=>
      object(stdClass)#4 (1) {
        ["Four"]=>
        object(stdClass)#5 (1) {
          ["Five"]=>
          object(stdClass)#6 (1) {
            ["Six"]=>
            object(stdClass)#7 (1) {
              ["Seven"]=>
              object(stdClass)#8 (1) {
                ["Eight"]=>
                object(stdClass)#9 (1) {
                  ["Nine"]=>
                  object(stdClass)#10 (1) {
                    ["Ten"]=>
                    object(stdClass)#11 (1) {
                      ["Eleven"]=>
                      object(stdClass)#12 (1) {
                        ["Twelve"]=>
                        object(stdClass)#13 (1) {
                          ["Thirteen"]=>
                          object(stdClass)#14 (1) {
                            ["Fourteen"]=>
                            object(stdClass)#15 (1) {
                              ["Fifteen"]=>
                              object(stdClass)#16 (1) {
                                ["Sixteen"]=>
                                object(stdClass)#17 (1) {
                                  ["Seventeen"]=>
                                  object(stdClass)#18 (1) {
                                    ["Eighteen"]=>
                                    array(3) {
                                      [0]=>
                                      int(1)
                                      [1]=>
                                      int(2)
                                      [2]=>
                                      int(3)
                                    }
                                  }
                                }
                              }
                            }
                          }
                        }
                      }
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}
string(208) "{"One":{"Two":{"Three":{"Four":{"Five":{"Six":{"Seven":{"Eight":{"Nine":{"Ten":{"Eleven":{"Twelve":{"Thirteen":{"Fourteen":{"Fifteen":{"Sixteen":{"Seventeen":{"Eighteen":{"Nineteen":[1,2,3]}}}}}}}}}}}}}}}}}}}"
NULL