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;")
}
mysqli_error
Description
Procedural style:
string mysqli_error ( mysqli link )Object oriented style (property)
class mysqli {string error
}
The mysqli_error() function is identical to the corresponding mysqli_errno() function in every way, except instead of returning an integer error code the mysqli_error() function will return a string representation of the last error to occur for the database connection represented by the link parameter. If no error has occured, this function will return an empty string.
范例
例子 2. Procedural style
|
上例将输出：
Errormessage: Unknown system variable 'a' |
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User Contributed Notes
se (at) brainbits (dot) net
20-Apr-2006 08:22
20-Apr-2006 08:22
information at saunderswebsolutions dot com
24-Jan-2006 06:37
24-Jan-2006 06:37
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.
information at saunderswebsolutions dot com
13-Jan-2006 06:52
13-Jan-2006 06:52
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}
paul ate santasoft doit com
29-Jul-2005 09:50
29-Jul-2005 09:50
When migrating to PHP 5 from PHP 4, an important sticky note on the brain:
PHP 4 would default to the current connection (last opened connection) with mysql_error(). PHP 5 & mysqli, on the other hand, requires the link to be specified as in mysqli_error($link).
So if you are migrating and get a blank screen and don't know why, check your mysqli_* statements to ensure they include the $link if needed.
examples:
PHP 4:
<?php
$link = mysql_connect('localhost',''uid','pw');
$sql = 'some bad query';
$result = mysql_query($sql);
if (!mysql_num_rows($result)) {
echo(mysql_error());
} else {
echo('It Worked!!!!!!');
}
?>
PHP 5:
<?php
$link = mysqli_connect('localhost',''uid','pw');
$sql = 'some bad query';
$result = mysqli_query($link,$sql); // remember to include the link on queries too
if (!mysqli_num_rows($result)) {
echo(mysqli_error($link)); // aha!
} else {
echo('It Worked!!!!!!');
}
?>