PHP mysqli: error() Function
mysqli_error() function / mysqli::$error
The mysqli_error() function / mysqli::$error returns the last error description for the most recent function call, if any.
Syntax:
Object oriented style
string $mysqli->error;
Procedural style
string mysqli_error ( mysqli $link )
Parameter:
Name | Description | Required/Optional |
---|---|---|
link | A link identifier returned by mysqli_connect() or mysqli_init() | Required for procedural style only and Optional for Object oriented style |
Usage: Procedural style
mysqli_error(connection);
Parameter:
Name | Description | Required/Optional |
---|---|---|
connection | Specifies the MySQL connection to use. | Required |
Return value:
A string that describes the error. An empty string if no error occurred.
Version: PHP 5, PHP 7
Example of object oriented style:
<?php
$mysqli = new mysqli("localhost", "user1", "datasoft123", "hr");
/* check connection */
if ($mysqli->connect_errno) {
printf("Connect failed: %s\n", $mysqli->connect_error);
exit();
}
if (!$mysqli->query("SET a=1")) {
printf("Errormessage: %s\n", $mysqli->error);
}
/* close connection */
$mysqli->close();
?>
Output:
Errormessage: Unknown system variable 'a'
Example of 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("Errormessage: %s\n", mysqli_error($link));
}
/* close connection */
mysqli_close($link);
?>
Output:
Errormessage: Unknown system variable 'a'
Example:
<?php
$con=mysqli_connect("localhost","user1","datasoft123","hr");
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
// Perform a query, check for error
if (!mysqli_query($con,"INSERT INTO employees (First_Name) VALUES ('David')"))
{
echo("Errorcode: " . mysqli_errno($con));
}
mysqli_close($con);
?>
Sample Output:
Errorcode: 1146
See also
Previous: error_list
Next: field_count
PHP: Tips of the Day
Getting all defined constants
To get all defined constants including those created by PHP use the get_defined_constants function:
Example:
<?php $constants = get_defined_constants(); var_dump($constants); // pretty large list
Output:
array(2250) { ["E_ERROR"]=> int(1) ["E_RECOVERABLE_ERROR"]=> int(4096) ["E_WARNING"]=> ..... ..... resource(1) of type (stream) ["STDOUT"]=> resource(2) of type (stream) ["STDERR"]=> resource(3) of type (stream) }
To get only those constants that were defined by your app call the function at the beginning and at the end of your script (normally after the bootstrap process):
<?php $constants = get_defined_constants(); define("HELLO", "hello"); define("WORLD", "world"); $new_constants = get_defined_constants(); $myconstants = array_diff_assoc($new_constants, $constants); var_export($myconstants);
Output:
array ( 'HELLO' => 'hello', 'WORLD' => 'world', )
It's sometimes useful for debugging
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