添加WHERE语句后，Gridview搜索停止工作

I have a grid view on my page. The grid gets filled from my database. I have build a search in my script, so when I type the number, name or price I get the correct data.

My SQL query to get information is the following:

 $sql = "SELECT id, name, price FROM employees";

Now I want to extend my script and the relevant information for a specific user. But when I add a WHERE statement to my SQL query, the search function stops working

This is the SQL query I need:

 $sql = "SELECT id, name, price FROM employees WHERE user_id='1'";

I dont know what is wrong with this. This query shows me the right data, but the search function stops working. I also tried this SQL query in phpMyAdmin and nothing is wrong with it.

Can someone help me with this problem. I really dont know what is wrong:

Here is the script I am using to get information from my database. The SQL query is on line 24: -- response.php --

<?php
 include_once("connection.php");

 $params = $columns = $totalRecords = $data = array();

 $params = $_REQUEST;

 $columns = array( 
 0 =>'id',
 1 =>'name', 
 2 => 'price',
 3 => 'user_id'
 );

 $where = $sqlTot = $sqlRec = "";

 if( !empty($params['search']['value']) ) {   
  $where .=" WHERE ";
  $where .=" ( id LIKE '".$params['search']['value']."%' ";    
  $where .=" OR name LIKE '".$params['search']['value']."%' ";
  $where .=" OR price LIKE '".$params['search']['value']."%')";
 }

 $sql = "SELECT id, name, price FROM employees WHERE user_id='1'";
 $sqlTot .= $sql;
 $sqlRec .= $sql;
 if(isset($where) && $where != '') {
  $sqlTot .= $where;
  $sqlRec .= $where;
 }

 $sqlRec .=  " ORDER BY ". $columns[$params['order'][0]['column']]."   ".$params['order'][0]['dir']."  LIMIT ".$params['start']." ,".$params['length']." ";

 $queryTot = mysqli_query($conn, $sqlTot) or die("database error:". mysqli_error($conn));

 $totalRecords = mysqli_num_rows($queryTot);

 $queryRecords = mysqli_query($conn, $sqlRec) or die("error to fetch employees data");

 while( $row = mysqli_fetch_row($queryRecords) ) { 
  $data[] = $row;
 }  

 $json_data = array(
 "draw"            => intval( $params['draw'] ),   
 "recordsTotal"    => intval( $totalRecords ),  
 "recordsFiltered" => intval($totalRecords),
 "data"            => $data
 );

 echo json_encode($json_data);
?>

Edit 1:

Now I have:

 if( !empty($params['search']['value']) ) {   
  $where .=" WHERE ";
  $where .=" ( id LIKE '".$params['search']['value']."%' ";    
  $where .=" OR name LIKE '".$params['search']['value']."%' ";
  $where .=" OR price LIKE '".$params['search']['value']."%') AND user_id='1'

 $sql = "SELECT id,name,price FROM customers";

When I run this, I get a grid-view without user_id='1'and a search function with user_id='1'. I need user_id='1' in both of them.

if $params is not empty you have two where in sql this is wrong

 if( !empty($params['search']['value']) ) {   
  $where .=" WHERE ";
  $where .=" ( id LIKE '".$params['search']['value']."%' ";    
  $where .=" OR name LIKE '".$params['search']['value']."%' ";
  $where .=" OR price LIKE '".$params['search']['value']."%')";
 }

  $sql = "SELECT id, name, price FROM employees WHERE user_id='1'";

......
// here you assign the firts where  by $sql 
$sqlTot .= $sql;
// here you assign the second where by eval $param
if(isset($where) && $where != '') {
 $sqlTot .= $where;
 $sqlRec .= $where;
}

I suggestio syou should use this setting

if( !empty($params['search']['value']) ) {   
  $where .=" WHERE ";
  $where .=" ( id LIKE '".$params['search']['value']."%' ";    
  $where .=" OR name LIKE '".$params['search']['value']."%' ";
  $where .=" OR price LIKE '".$params['search']['value']."%')  ";

}
if (!empty($where) ) {

   $where .= "AND user_id='1' ";
} else {
     $where .= "WHERE  user_id='1' ";
}


$sql = "SELECT id,name,price FROM customers";