Why Am I Getting the 'mysql_fetch_array() expects parameter 1 to be resource, boolean given' Error in PHP?

Error Message: "mysql_fetch_array()/mysql_fetch_assoc()/mysql_fetch_row()/mysql_num_rows etc... expects parameter 1 to be resource, boolean given"

This error occurs when calling a function that expects a resource as the first parameter, but a boolean value is passed instead. In this specific case, it indicates that the query failed, resulting in a false value being returned.

Solution:

To resolve this issue, check the result of the MySQL query before passing it to the data retrieval functions. In PHP's mysql_ extension, use mysql_query() and test its return value. If the query fails, you can handle the error accordingly or issue a trigger.

Here's an example with improved error handling:

<?php
$username = mysql_real_escape_string($_POST['username']);
$password = $_POST['password'];

$result = mysql_query("SELECT * FROM Users WHERE UserName LIKE '$username'");

if ($result === FALSE) { 
    trigger_error(mysql_error(), E_USER_ERROR);
}

while ($row = mysql_fetch_array($result))
{
    echo $row['FirstName'];
}
?>

By using mysql_real_escape_string() to sanitize user input, you can also prevent SQL injection attacks, which can be a cause of query failure.

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