mysql real escape string not letting insert data

Question

i have a form for job post now whenever user enters data and i use mysql real escape string it insert blank data in mysql what could be the reason? here is the code of site. the thing is i can't trust user input that's why i want to use mysql_real_escape string . i have been trying and changing codes from 2 hours but none of them gave me good result!

     function test_input($data) {


$data = trim($data);
   $data = stripslashes($data);
  $data = mysql_real_escape_string($data);
  return $data;
} 
    $userid1 = $_SESSION['username2'];
    $email= test_input($_POST['email']);
     $salary= test_input($_POST['salary']);
    $job_title = test_input($_POST['jtitle']);
     $company = test_input($_POST['company']);
     $company = mysql_real_escape_string($_POST['company']);
    $location = test_input($_POST['location']);
    $jobtype = test_input($_POST['jobtype']);
     $description = test_input($_POST['description']);
    $closingdate = test_input($_POST['closingdate']);
    $application = test_input($_POST['application']);
    $phone = test_input($_POST['phone']);
    $company_description = test_input($_POST['company_description']);

     $co_video = test_input($_POST['co_video']);
    $website = test_input($_POST['website']);
    $fbid = test_input($_POST['fbid']);
     $twid = test_input($_POST['twid']);

function create_slug($string){     
        $replace = '-';         
        $string = strtolower($string);     

        //replace / and . with white space     
        $string = preg_replace("/[\/\.]/", " ", $string);     
        $string = preg_replace("/[^a-z0-9_\s-]/", "", $string);     

        //remove multiple dashes or whitespaces     
        $string = preg_replace("/[\s-]+/", " ", $string);     

        //convert whitespaces and underscore to $replace     
        $string = preg_replace("/[\s_]/", $replace, $string);     

        //limit the slug size     
        $string = substr($string, 0, 100);     

        //slug is generated     
        return $string; 
    }     

    $string = $job_title; 
    $slug = create_slug($string);
$query = mysqli_query($con, "SELECT * FROM `job` WHERE `url` LIKE '".$slug."%'");      
$exists = mysqli_fetch_array(mysqli_query($con,"SELECT count(id) as notify FROM `job` where `url` LIKE '".$slug."%'")); 
    $notify = $exists['notify'];
    if ($notify > 0)
{
    $new_number = $notify + 1;
    $newslug = $slug."-".$new_number;
$run = mysqli_query($con, "INSERT INTO `job` (`email`, `salary`, `username`, `job_title`, `company_name`, `location`, `job_type`, `description`, `phone`, `closing_date`, `application_url`, `company_description`, `video`, `website`, `fb`, `tw`, `category`, `url`) VALUES ('".$email."', '".$salary."',  '".$userid1."', '".$job_title."', '".$company."', '".$location."', '".$jobtype."', '".$description."', '".$phone."', '".$closingdate."', '".$application."', '".$company_description."', '".$co_video."', '".$website."', '".$fbid."', '".$twid."', '".$lt."' , '".$newslug."')");
} else{ 
$run = mysqli_query($con, "INSERT INTO `job` (`email`, `salary`, `username`, `job_title`, `company_name`, `location`, `job_type`, `description`, `phone`, `closing_date`, `application_url`, `company_description`, `video`, `website`, `fb`, `tw`, `category`, `url`) VALUES ('".$email."', '".$salary."',  '".$userid1."', '".$job_title."', '".$company."', '".$location."', '".$jobtype."', '".$description."', '".$phone."', '".$closingdate."', '".$application."', '".$company_description."', '".$co_video."', '".$website."', '".$fbid."', '".$twid."', '".$lt."', '".$slug."')"); 

Answer 1

well i think you have to use two parameters in mysqli_real_escape_string but first you have to create the first parameter by setting connection with database it should be like

<?php
//for setting up connection with database
$conn=mysqli_connect('yourhostname','your mysql user name','your mysql password','your database');
//than try using this parameter in mysqlirealescapestring
$data=mysqli_real_escape_string($conn,$data);

?>

i hope that this could work