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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

PHP Function Reference

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Next: field_count



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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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