PHP - Manual: mysqli::$error

2024-11-14

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mysqli::$error

mysqli_error

(PHP 5, PHP 7, PHP 8)

mysqli::$error -- mysqli_error — Returns a string description of the last error

说明

面向对象风格

string $mysqli->error;

过程化风格

mysqli_error(mysqli $mysql): string

Returns the last error message for the most recent MySQLi function call that can succeed or fail.

参数

mysql: 仅以过程化样式：由mysqli_connect() 或 mysqli_init() 返回的 mysqli 对象。

返回值

A string that describes the error. An empty string if no error occurred.

范例

示例 #1 $mysqli->error example

面向对象风格


<?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("Error message: %s\n", $mysqli->error);
}

/* close connection */
$mysqli->close();
?>

过程化风格


<?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($link, "SET a=1")) {
    printf("Error message: %s\n", mysqli_error($link));
}

/* close connection */
mysqli_close($link);
?>

以上例程会输出：

Error message: Unknown system variable 'a'

参见

mysqli_connect_errno() - Returns the error code from last connect call
mysqli_connect_error() - Returns a description of the last connection error
mysqli_errno() - 返回最近函数调用的错误代码
mysqli_sqlstate() - 返回上一次 SQL 操作的 SQLSTATE 错误信息

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User Contributed Notes 6 notes

down

information at saunderswebsolutions dot com ¶

16 years ago


The mysqli_sql_exception class is not available to PHP 5.05

I used this code to catch errors 
<?php
$query = "SELECT XXname FROM customer_table ";
$res = $mysqli->query($query);

if (!$res) {
   printf("Errormessage: %s\n", $mysqli->error);
}

?>
The problem with this is that valid values for $res are: a mysqli_result object , true or false
This doesn't tell us that there has been an error with the sql used.
If you pass an update statement, false is a valid result if the update fails.

So, a better way is:
<?php
$query = "SELECT XXname FROM customer_table ";
$res = $mysqli->query($query);

if (!$mysqli->error) {
   printf("Errormessage: %s\n", $mysqli->error);
}

?>

This would output something like:
Unexpected PHP error [mysqli::query() [<a href='function.query'>function.query</a>]: (42S22/1054): Unknown column 'XXname' in 'field list'] severity [E_WARNING] in [G:\database.php] line [249]

Very frustrating as I wanted to also catch the sql error and print out the stack trace. 

A better way is:

<?php
mysqli_report(MYSQLI_REPORT_OFF); //Turn off irritating default messages

$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

$query = "SELECT XXname FROM customer_table ";
$res = $mysqli->query($query);

if ($mysqli->error) {
    try {    
        throw new Exception("MySQL error $mysqli->error <br> Query:<br> $query", $msqli->errno);    
    } catch(Exception $e ) {
        echo "Error No: ".$e->getCode(). " - ". $e->getMessage() . "<br >";
        echo nl2br($e->getTraceAsString());
    }
}

//Do stuff with the result
?>
Prints out something like:
Error No: 1054
Unknown column 'XXname' in 'field list'
Query: 
SELECT XXname FROM customer_table

#0 G:\\database.php(251): database->dbError('Unknown column ...', 1054, 'getQuery()', 'SELECT XXname F...')
#1 G:\data\WorkSites\1framework5\tests\dbtest.php(29): database->getString('SELECT XXname F...')
#2 c:\PHP\includes\simpletest\runner.php(58): testOfDB->testGetVal()
#3 c:\PHP\includes\simpletest\runner.php(96): SimpleInvoker->invoke('testGetVal')
#4 c:\PHP\includes\simpletest\runner.php(125): SimpleInvokerDecorator->invoke('testGetVal')
#5 c:\PHP\includes\simpletest\runner.php(183): SimpleErrorTrappingInvoker->invoke('testGetVal')
#6 c:\PHP\includes\simpletest\simple_test.php(90): SimpleRunner->run()
#7 c:\PHP\includes\simpletest\simple_test.php(498): SimpleTestCase->run(Object(HtmlReporter))
#8 c:\PHP\includes\simpletest\simple_test.php(500): GroupTest->run(Object(HtmlReporter))
#9 G:\all_tests.php(16): GroupTest->run(Object(HtmlReporter))

This will actually print out the error, a stack trace and the offending sql statement. Much more helpful when the sql statement is generated somewhere else in the code.

down

se (at) brainbits (dot) net ¶

16 years ago


The decription "mysqli_error -- Returns a string description of the LAST error" is not exactly that what you get from mysqli_error. You get the error description from the last mysqli-function, not from the last mysql-error.

If you have the following situation

if (!$mysqli->query("SET a=1")) {
   $mysqli->query("ROLLBACK;")
   printf("Errormessage: %s\n", $mysqli->error);
}

you don't get an error-message, if the ROLLBACK-Query didn't failed, too. In order to get the right error-message you have to write:

if (!$mysqli->query("SET a=1")) {
   printf("Errormessage: %s\n", $mysqli->error);
   $mysqli->query("ROLLBACK;")
}

down

callforeach at gmail dot com ¶

7 years ago


I had to set mysqli_report(MYSQLI_REPORT_ALL) at the begin of my script to be able to catch mysqli errors within the catch block of my php code.

Initially, I used the below code to throw and subsequent catch mysqli exceptions

<?php
try {
   $mysqli = new mysqli('localhost','root','pwd','db');
    if ($mysqli->connect_errno) 
        throw new Exception($mysqli->connect_error);

} catch (Exception $e) {
     echo $e->getMessage();
}

I realized the exception was being thrown before the actual throw statement and hence the catch block was not being called.

My current code looks like
mysqli_report(MYSQLI_REPORT_ALL) ;
try {
      $mysqli = new mysqli('localhost','root','pwd','db');
      /* I don't need to throw the exception, it's being thrown automatically */

} catch (Exception $e) {
  echo $e->getMessage();
}

This works fine and I'm able to trap all mysqli errors

down

asmith16 at littlesvr dot ca ¶

8 years ago


Please note that the string returned may contain data initially provided by the user, possibly making your code vulnerable to XSS. 

So even if you escape everything in your SQL query using mysqli_real_escape_string(), make sure that if you plan to display the string returned by mysqli_error() you run that string through htmlspecialchars().

As far as I can tell the two escape functions don't escape the same characters, which is why you need both (the first for SQL and the second for HTML/JS).

down

-6

information at saunderswebsolutions dot com ¶

16 years ago


Hi, you can also use the new mysqli_sql_exception to catch sql errors.
Example:
<?php
//set up $mysqli_instance here..
$Select = "SELECT xyz FROM mytable ";
try {
    $res = $mysqli_instance->query($Select);
}catch (mysqli_sql_exception $e) {
    print "Error Code <br>".$e->getCode();
    print "Error Message <br>".$e->getMessage();
    print "Strack Trace <br>".nl2br($e->getTraceAsString());
}

?>
Will print out something like
Error Code: 0
Error Message
No index used in query/prepared statement select sess_value from frame_sessions where sess_name = '5b85upjqkitjsostvs6g9rkul1'
Strack Trace:
#0 G:\classfiles\lib5\database.php(214): mysqli->query('select sess_val...')
#1 G:\classfiles\lib5\Session.php(52): database->getString('select sess_val...')
#2 [internal function]: sess_read('5b85upjqkitjsos...')
#3 G:\classfiles\includes.php(50): session_start()
#4 G:\tests\all_tests.php(4): include('G:\data\WorkSit...')
#5 {main}

down

-7

Anonymous ¶

2 years ago


mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
try {
                $this->connection = mysqli_connect($hostname,$username,$password, $dbname);
} catch (Exception $e) {
                echo "Errno: " . mysqli_connect_errno() . PHP_EOL;
                echo "Text error: " . mysqli_connect_error() . PHP_EOL;
                exit;
}

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mysqli::$error

mysqli_error

说明

参数

返回值

范例

参见

User Contributed Notes 6 notes