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Fatal error: Uncaught mysqli_sql_exception: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '<?rows['id']?>' at line 1 in C:\xampp\htdocs\SIU\updatess.php:12 Stack trace: #0 C:\xampp\htdocs\SIU\updatess.php(12): mysqli_query(Object(mysqli), 'SELECT * FROM p...') #1 C:\xampp\htdocs\SIU\updates.php(1): include('C:\\xampp\\htdocs...') #2 {main} thrown in C:\xampp\htdocs\SIU\updatess.php on line 12


What I have tried:

<?php
if (isset($_GET['id'])) {
    include "siudb.php";
    function validate($data) {
        $data = trim($data);
        $data = stripslashes($data);
        $data = htmlspecialchars($data);
        return $data;
    }
    $id = validate($_GET['id']);
    $sql = "SELECT * FROM project_tbl WHERE ID=$id";
    $result = mysqli_query($conn, $sql);
    if (mysqli_num_rows($result) > 0) {
        $row = mysqli_fetch_assoc($result);
    } else {
        header("Location: dei.php");
    }
} else {
    header("Location: dei.php");
} ?>
Posted
Updated 14-Aug-22 18:13pm
Comments
Richard MacCutchan 15-Aug-22 4:12am    
The error message suggests that your id field is the string "", which SQL is rejecting.

1 solution

Don't do it like that! Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:
SQL
SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'
The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:
SQL
SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'
Which SQL sees as three separate commands:
SQL
SELECT * FROM MyTable WHERE StreetAddress = 'x';
A perfectly valid SELECT
SQL
DROP TABLE MyTable;
A perfectly valid "delete the table" command
SQL
--'
And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

Chances are that it what is causing your problem and that fixing it throughout your app will cure it at the same time.
 
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