mysqli::get_warnings()

(PHP 5 >= 5.1.0, PHP 7)

Get result of SHOW WARNINGS

说明

面向对象风格
mysqli::get_warnings(void): mysqli_warning

过程化风格
mysqli_get_warnings(mysqli$link): mysqli_warning

Warning

本函数还未编写文档，仅有参数列表。

With a bit of rooting about with reflection, I spotted that the mysqli_warning class has a next() function, so I tried calling it and it does indeed progress through the available warnings! Following on from my earlier example:
<?php
$r = mysqli_query($db, "INSERT INTO blah SET z = '1'");
$j = mysqli_warning_count($db);
if ($j > 0) {
  $e = mysqli_get_warnings($db);
  for ($i = 0; $i < $j; $i++) {
    var_dump($e);
    $e->next();
  }
}
?>
There is a simple way of traversing the warnings:
<?php
$r = mysqli_query($db, "INSERT INTO blah SET z = '1'");
if (mysqli_warning_count($db)) {
  $e = mysqli_get_warnings($db);
  do {
    echo "Warning: $e->errno: $e->message\n";
  } while ($e->next());
}
?>

Take note:
Calling this function will change the output of mysqli_affected_rows if any warnings are returned. So if you're using mysqli_affected_rows in your application, make sure to call it before calling mysqli_get_warnings.

I'm not sure how useful this function is as implemented. Take this example:
CREATE TABLE `blah` (
 `x` varchar(100) NOT NULL,
 `y` varchar(100) NOT NULL,
 `z` varchar(100) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
INSERT INTO blah SET z = '1';
Query OK, 1 row affected, 2 warnings (0.00 sec)
mysql> show warnings;
+---------+------+----------------------------------------+
| Level  | Code | Message                |
+---------+------+----------------------------------------+
| Warning | 1364 | Field 'x' doesn't have a default value | 
| Warning | 1364 | Field 'y' doesn't have a default value | 
+---------+------+----------------------------------------+
Doing the same from PHP using mysqli_get_warnings(), you get this instead:
object(mysqli_warning)#4 (3) {
 ["message"]=>
 string(38) "Field 'x' doesn't have a default value"
 ["sqlstate"]=>
 string(5) "HY000"
 ["errno"]=>
 int(1364)
}
i.e. it only returns the first warning. I suspect it should return an array of these objects rather than just one. At least you know what the return value looks like now, since the docs don't say!