PHP error and mysqli_error()

This article is created to cover the two topics of PHP, namely:

• error
• mysqli_error()

Both are used to return the description of the error (if any) by the most recent function call. The only difference is that the error uses PHP mysqli object-oriented script, whereas mysqli_error() uses PHP mysqli procedural script.

PHP error

The PHP error returns the description of the error (if any) by the most recent function call in PHP mysqli object-oriented style. For example:

<?php
   $driver = new mysqli_driver();
   $driver->report_mode = MYSQLI_REPORT_OFF;
   
   $servername = "localhost";
   $username = "root";
   $password = "";
   
   $conn = new mysqli($servername, $username, $password);
   
   if($conn->connect_errno)
   {
      echo "Database connection failed!<BR>";
      echo "Reason: ", $conn->connect_error;
      exit();
   }
   
   $table = "myTable";
   $sql = "INSERT INTO $table (Name, City) VALUES ('Jackson', 'Vancouver')";
   $qry = $conn->query($sql);
   if($qry)
   {
      // block of code to process further
      // if everything is fine
   }
   else
   {
      echo "Error occurred while executing the query.<BR>";
      echo "Reason: ", $conn->error;
   }
   $conn->close();
?>

The output produced by the above PHP example on error is shown in the snapshot given below:

That is:

Error occurred while executing the query.
Reason: No database selected

Because, while opening the connection, I did not provide the database. Therefore, while executing the query to insert some data into the table named myTable, it has not executed because the database has not been selected.

Note: The mysqli_driver() function is used to modify the error reporting mode in object-oriented style.

Note: The mysqli() function is used to open a connection to the MySQL database server in object-oriented style.

Note: The new keyword is used to create a new object.

Note: The connect_errno is used to get or return the error code (if any) from the last connect call in object-oriented style.

Note: The connect_error is used to get the error description (if any) from the last connection in object-oriented style.

Note: The query() function is used to perform queries on the MySQL database in object-oriented style.

Note: The close() function is used to close an opened connection in object-oriented style.

Now let me insert and select the database, say codescracker, and re-execute the above PHP script:

<?php
   $driver = new mysqli_driver();
   $driver->report_mode = MYSQLI_REPORT_OFF;
   
   $conn = new mysqli("localhost", "root", "", "codescracker");
   
   if(!$conn->connect_errno)
   {
      if(!$conn->query("INSERT INTO myTable (Name, City) VALUES ('Jackson', 'Vancouver')"))
      {
         echo "Error occurred while executing the query.<BR>";
         echo "Reason: ", $conn->error;
      }
   }
   $conn->close();
?>

Since the table myTable is not available in my database named codescracker. Therefore, the output should be:

Error occurred while executing the query.
Reason: Table 'codescracker.mytable' doesn't exist

Saying that the table mytable does not exist in the database codescracker.

The following two statements:

$driver = new mysqli_driver();
$driver->report_mode = MYSQLI_REPORT_OFF;

are used to turn off the error reporting and show you the custom error message defined by the developer.

PHP error Syntax

The syntax of an "error" in PHP is:

connectionVariable -> error

PHP mysqli_error()

The mysqli_error() returns the description of the error (if any), by the most recent function call in PHP mysqli procedural style. For example:

<?php
   mysqli_report(MYSQLI_REPORT_OFF);
   
   $conn = mysqli_connect("localhost", "root", "", "codescracker");
   
   if(!mysqli_connect_errno())
   {
      if(!mysqli_query($conn, "INSERT INTO myTable (Name, City) VALUES ('Jackson', 'Vancouver')"))
      {
         echo "Error occurred while executing the query.<BR>";
         echo "Reason: ", mysqli_error($conn);
      }
   }
   mysqli_close($conn);
?>

You will get the same output as the previous one.

Note: The mysqli_report() function is used to modify the error reporting mode in procedural style.

Note: The mysqli_connect() function is used to open a connection to the MySQL database server in procedural style.

Note: The mysqli_connect_errno() function is used to get or return the error code (if any) from the last connect call in procedural style.

Note: The mysqli_query() function is used to perform queries on the MySQL database in procedural style.

Note: The mysqli_close() function is used to close an opened connection to the MySQL database in procedural style.

PHP mysqli_error() Syntax

The syntax of the mysqli_error() function in PHP is:

mysqli_error(connectionVariable)

PHP Online Test