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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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PHP: Tips of the Day

PHP: PHP function overloading

You cannot overload PHP functions. Function signatures are based only on their names and do not include argument lists, so you cannot have two functions with the same name. Class method overloading is different in PHP than in many other languages. PHP uses the same word but it describes a different pattern.

You can, however, declare a variadic function that takes in a variable number of arguments. You would use func_num_args() and func_get_arg() to get the arguments passed, and use them normally.

For example:

function myFunc() {
    for ($i = 0; $i < func_num_args(); $i++) {
        printf("Argument %d: %s\n", $i, func_get_arg($i));
    }
}

/*
Argument 0: a
Argument 1: 2
Argument 2: 3.5
*/
myFunc('a', 2, 3.5);

Ref : https://bit.ly/2WnjWAt