mysqli_result::fetch_assoc()

(PHP 5, PHP 7)

Fetch a result row as an associative array

说明

面向对象风格
mysqli_result::fetch_assoc(void): array

过程化风格
mysqli_fetch_assoc(mysqli_result$result): array

Returns an associative array that corresponds to the fetched row or NULL if there are no more rows.

Note:此函数返回的字段名大小写敏感。

Note:此函数将 NULL 字段设置为 PHP NULL值。

参数

$result: 仅以过程化样式：由mysqli_query()，mysqli_store_result()或mysqli_use_result()返回的结果集标识。

返回值

Returns an associative array of strings representing the fetched row in the result set, where each key in the array represents the name of one of the result set's columns or NULL if there are no more rows in resultset.

If two or more columns of the result have the same field names, the last column will take precedence. To access the other column(s)of the same name, you either need to access the result with numeric indices by using mysqli_fetch_row() or add alias names.

范例

Example #1 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();
}
$query = "SELECT Name, CountryCode FROM City ORDER by ID DESC LIMIT 50,5";
if ($result = $mysqli->query($query)) {
    /* fetch associative array */
    while ($row = $result->fetch_assoc()) {
        printf ("%s (%s)\n", $row["Name"], $row["CountryCode"]);
    }
    /* free result set */
    $result->free();
}
/* close connection */
$mysqli->close();
?>

Example #2 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();
}
$query = "SELECT Name, CountryCode FROM City ORDER by ID DESC LIMIT 50,5";
if ($result = mysqli_query($link, $query)) {
    /* fetch associative array */
    while ($row = mysqli_fetch_assoc($result)) {
        printf ("%s (%s)\n", $row["Name"], $row["CountryCode"]);
    }
    /* free result set */
    mysqli_free_result($result);
}
/* close connection */
mysqli_close($link);
?>

以上例程会输出：

Pueblo (USA)
Arvada (USA)
Cape Coral (USA)
Green Bay (USA)
Santa Clara (USA)

Example #3 A mysqli_result example comparing iterator usage

<?php
$c = mysqli_connect('127.0.0.1','user', 'pass');
// Using iterators (support was added with PHP 5.4)
foreach ( $c->query('SELECT user,host FROM mysql.user') as $row ) {
    printf("'%s'@'%s'\n", $row['user'], $row['host']);
}
echo "\n==================\n";
// Not using iterators
$result = $c->query('SELECT user,host FROM mysql.user');
while ($row = $result->fetch_assoc()) {
    printf("'%s'@'%s'\n", $row['user'], $row['host']);
}
?>

以上例程的输出类似于：

'root'@'192.168.1.1'
'root'@'127.0.0.1'
'dude'@'localhost'
'lebowski'@'localhost'
==================
'root'@'192.168.1.1'
'root'@'127.0.0.1'
'dude'@'localhost'
'lebowski'@'localhost'

参见

mysqli_fetch_array() Fetch a result row as an associative, a numeric array, or both
mysqli_fetch_row() Get a result row as an enumerated array
mysqli_fetch_object() Returns the current row of a result set as an object
mysqli_query() 对数据库执行一次查询
mysqli_data_seek() Adjusts the result pointer to an arbitrary row in the result

I often like to have my results sent elsewhere in the format of an array (although keep in mind that if you just plan on traversing through the array in another part of the script, this extra step is just a waste of time).
This is my one-liner for transforming a mysqli_result set into an array.
<?php
$sql = new MySQLi($host, $username, $password, $database);
$result = $sql->query("SELECT * FROM `$table`;");
for ($set = array (); $row = $result->fetch_assoc(); $set[] = $row);
print_r($set);
?>
Outputs:
Array
(
  [0] => Array
    (
      [id] => 1
      [field2] => a
      [field3] => b
    ),
  [1] => Array
    (
      [id] => 2
      [field2] => c
      [field3] => d
    )
)
I use other variations to adapt to the situation, i.e. if I am selecting only one field:
<?php
$sql = new MySQLi($host, $username, $password, $database);
$result = $sql->query("SELECT `field2` FROM `$table`;");
for ($set = array (); $row = $result->fetch_assoc(); $set[] = $row['field2']);
print_r($set);
?>
Outputs:
Array
(
  [0] => a
  [1] => c
)
Or, to make the array associative with the primary index (code assumes primary index is the first field in the table):
<?php
$sql = new MySQLi($host, $username, $password, $database);
$result = $sql->query("SELECT * FROM `$table`;");
for ($set = array (); $row = $result->fetch_assoc(); $set[array_shift($row)] = $row);
print_r($set);
?>
Outputs:
Array
(
  [1] => Array
    (
      [field2] => a
      [field3] => b
    ),
  [2] => Array
    (
      [field2] => c
      [field3] => d
    )
)

IMPORTANT NOTE:
If you were used to using code like this:
<?php
while(false !== ($row = mysql_fetch_assoc($result)))
{
  //...
}
?>
You must change it to this for mysqli:
<?php
while(null !== ($row = mysqli_fetch_assoc($result)))
{
  //...
}
?>
The former will cause your script to run until max_execution_time is reached.

when you fetch the data from the query variable 
and try to fetch it again in another part of the script
from the same query variable , 
when you try to echo all data you have fetched,
it will not echo the data you have used in the first fetch 
(it will exceed the results you have used in the first fetch).......
Example :
<?php
$connect = new mysqli("localhost","root","root","elshamy")
 or die (mysqli_error());
$query=$connect->query("SELECT * FROM users ORDER BY id ASC");
$first_fetch=$query->fetch_array(MYSQLI_ASSOC);
echo $first_fetch['id']."===>".$first_fetch['user_name']."\n--------------------\n";
while($row=$query->fetch_array(MYSQLI_ASSOC)){
/*it will exceed the first 
id&user_name value that 
you have use in the first fetch*/
echo $row['id']." ".$row['user_name']."<br/>"; 
}
?>
above example will echo :
1===>userA 
------------------------
2===>userB
3===>userC
4===>userD

The official example given here breaks a cardinal rule, and should be rectified.
while ($row = $result->fetch_assoc())...
...breaks the rule of "assignment in condition".
while (($x = $y->getZ()) !== false) or
while (($x = $y->getZ()) !== null)
...is the correct syntax.
Conditional statements should always check for a boolean

Be careful when using fetch_assoc instead of fetch_row. If two columns of the result have the same column name, even if they are prefixed with different table names in the query, only one of them will be retained in the result. This is because the prefix is dropped (either by mysql or by this function)
For example if the query is 
   select p1.name, p2.name 
   from person p1, friend, person p2
   where p1.id = friend.person1 and p2.id = friend.person2
the arrays returned by fetch_assoc will be of the form
{'name' => 'bob'}
{'name' => 'anna'}
and not (as expected)
{'p1.name' => 'bob', 'p2.name' => 'alice'}
{'p1.name' => 'anna', 'p2.name' => 'irla'}