Ajax always jumps to error, and doesn't work addslashes

Question

1.00/5 (1 vote)

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This code works. The comment works fine, but the result always goes to error on AJAX and displays 200 OK in the console window. Why is it that it jumps to an error instead of a success?

Another problem is that, despite using the addslashes function, the quotes are not handled and mysql error occurs.

What I have tried:

<?php
// php file for call $GLOBALS.
?>
<script type="text/javascript">

$(document).ready(function(){
   $(document.on('click', '.upload_comment', function(){
       let id = $(this).attr("id");
       let content = $("#comment-post-"+id).val();
       let text = $("#comment-textvalue-"+id).val();
       let customer = <?php echo $GLOBALS['user']; ?>;

       let object = {
          content: id,
          user: customer,
          comment: text
       }

       let jsonData = JSON.stringify(object);

       $.ajax({
          type: "POST",
          url:  "upload-comment.php",
          data: {data: jsonData},
          success: function( html ){
             $("ul#comment-"+id).append(html);
             $("#comment-textvalue-"+id).val("");
          },
          error: function( xhr ){  
             console.log(xhr.status+' '+xhr.statusText);
          }
        });
        return false;

   });
});
</script>

//upload-comment.php
if( isset( $_POST['data'] ) ){
  $data = json_decode( $_POST['data'] );

  foreach( $data as $value){
      $value = htmlentities( $value, ENT_QUOTES, "UTF-8" );
      $value = addslashes( $value );  
  }

  $conn = db_connect();
  $result = $conn->query{"select * from wc_comments") or die("access wc_comments failed: " . mysqli_error( $conn ) );
  if( $result ){
      $result = $conn->query("insert into wc_comments(content, author, date, comment") VALUES('".$data->{'content'}."', '".$data->{'user'}."', now(), '".$data->{'comment'}.'")")or die("insert failed: " . mysqli_error($conn));
     echo "<li class='comment'>".$comment."</li>";
  }
}

Posted 25-Apr-22 21:42pm

Chopin2001

Updated 25-Apr-22 22:41pm

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Comments

Richard Deeming 26-Apr-22 3:59am

Your code is vulnerable to SQL Injection[^]. NEVER use string concatenation/interpolation to build a SQL query. ALWAYS use a parameterized query.
PHP: SQL Injection - Manual[^]
PHP: Prepared statements and stored procedures - Manual[^]

Chopin2001 27-Apr-22 5:34am

Thanks for your comment.

1 solution

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Patrice T · Accepted Answer · 2022-04-25T22:41:00

Quote:
Another problem is that, despite using the addslashes function, the quotes are not handled and mysql error occurs.

I suspect you should correct quotes errors:

PHP

$result = $conn->query("insert into wc_comments(content, author, date, comment") VALUES('".$data->{'content'}."', '".$data->{'user'}."', now(), '".$data->{'comment'}.'")")or die("insert failed: " . mysqli_error($conn));

comment") VALUES should be comment) VALUES
.'")") should be ."')")

Never build an SQL query by concatenating strings. Sooner or later, you will do it with user inputs, and this opens door to a vulnerability named "SQL injection", it is dangerous for your database and error prone.
A single quote in a name and your program crash. If a user input a name like "Brian O'Conner" can crash your app, it is an SQL injection vulnerability, and the crash is the least of the problems, a malicious user input and it is promoted to SQL commands with all credentials.
SQL injection - Wikipedia[^]
SQL Injection[^]
SQL Injection Attacks by Example[^]
PHP: SQL Injection - Manual[^]
How can I explain SQL injection without technical jargon? - Information Security Stack Exchange[^]