You can also find the error codes for for example MySQL 5.5 here: http://dev.mysql.com/doc/refman/5.5/en/error-handling.html
(PHP 5, PHP 7)
mysqli::$errno -- mysqli_errno — Returns the error code for the most recent function call
Object oriented style
Procedural style
Returns the last error code for the most recent MySQLi function call that can succeed or fail.
Client error message numbers are listed in the MySQL errmsg.h header file, server error message numbers are listed in mysqld_error.h. In the MySQL source distribution you can find a complete list of error messages and error numbers in the file Docs/mysqld_error.txt.
link
Procedural style only: A link identifier returned by mysqli_connect() or mysqli_init()
An error code value for the last call, if it failed. zero means no error occurred.
Example #1 $mysqli->errno example
Object oriented style
<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");
/* check connection */
if ($mysqli->connect_errno) {
printf("Connect failed: %s\n", $mysqli->connect_error);
exit();
}
if (!$mysqli->query("SET a=1")) {
printf("Errorcode: %d\n", $mysqli->errno);
}
/* close connection */
$mysqli->close();
?>
Procedural style
<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "world");
/* check connection */
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
if (!mysqli_query($link, "SET a=1")) {
printf("Errorcode: %d\n", mysqli_errno($link));
}
/* close connection */
mysqli_close($link);
?>
The above examples will output:
Errorcode: 1193
You can also find the error codes for for example MySQL 5.5 here: http://dev.mysql.com/doc/refman/5.5/en/error-handling.html