Boolean False

Boolean False

Hi im new to Zoho and i am having a major problem creating estimates using php and curl. please tell me what i am doing wrong. i keep getting a 'boolean false'

<?php

$data = array(
      'send' => 'false',
      'ignore_auto_number_generation'   => 'true',
'authtoken' => 'AUTHTOKEN',
'JSONString' => '{
      "contact_persons": [
        "157691000000041090"
      ],
      "template_id": "15769100*****41077",
      "estimate_number": "EST-000001",
      "reference_number": "QRT-123456",
      "date": "2015-08-25",
      "expiry_date": "2015-08-27"
      "exchange_rate": 1.0,
      "discount": 0.0,
      "is_discount_before_tax": true,
      "discount_type": "item_level",
      "salesperson_name": "John Michael",
      "is_inclusive_tax": "false",
      "custom_fields": [
        {
          "index": 1,
          "value": "25 Aug 2015"
        }
      ],
      "line_items": [
        {
          "item_id": "157691*****0041080",
          "name": "Book1",
          "description": "book",
          "rate": 50.00,
          "item_order": 0,
          "quantity": 1.0,
          "discount": 0.0,
          "tax_id": "",
        }
      ],
      "notes": "Looking forward for your business.",
      "terms": "Terms and conditions apply.",
      "shipping_charge": 0.0,
      "adjustment": 0.0,
      "adjustment_description": "Adjustment"
    }',
"organization_id" => 'ORGID'
);

$curl = curl_init($url);

curl_setopt_array($curl, array(
 CURLOPT_POST => 1,
 CURLOPT_POSTFIELDS => $data,
 CURLOPT_RETURNTRANSFER => true
));

$estimate = curl_exec($curl);
    var_dump($estimate);
?>