# mysql_fetch_field

(PHP 4, PHP 5)

mysql_fetch_field — 从结果集中取得列信息并作为对象返回

警告

本扩展自 PHP 5.5.0 起已废弃，并在自 PHP 7.0.0 开始被移除。应使用 MySQLi 或 PDO_MySQL 扩展来替换之。参见 MySQL：选择 API 指南来获取更多信息。用以替代本函数的有：

- mysqli_fetch_field()
- PDOStatement::getColumnMeta()

### 说明

mysql_fetch_field(resource `$result`, int `$field_offset` = ?): object

返回一个包含字段信息的对象。

mysql_fetch_field() 可以用来从某个查询结果中取得字段的信息。如果没有指定字段偏移量，则下一个尚未被 mysql_fetch_field() 取得的字段被提取。

对象的属性为：

- name - 列名
- table - 该列所在的表名，which is the alias name if one is defined
- max_length - 该列最大长度
- not_null - 1，如果该列不能为 `null`
- primary_key - 1，如果该列是 primary key
- unique_key - 1，如果该列是 unique key
- multiple_key - 1，如果该列是 non-unique key
- numeric - 1，如果该列是 numeric
- blob - 1，如果该列是 BLOB
- type - 该列的类型
- unsigned - 1，如果该列是无符号数
- zerofill - 1，如果该列是 zero-filled

> 注意: 此函数返回的字段名大小写敏感。

示例 #1 mysql_fetch_field()

`<?php
mysql_connect('localhost:3306', $user, $password)
or die("Could not connect: " . mysql_error());
mysql_select_db("database");
$result = mysql_query("select * from table")
or die("Query failed: " . mysql_error());
/* get column metadata */
$i = 0;
while ($i < mysql_num_fields($result)) {
echo "Information for column $i:<br />\n";
$meta = mysql_fetch_field($result);
if (!$meta) {
echo "No information available<br />\n";
}
echo "<pre>
blob: $meta->blob
max_length: $meta->max_length
multiple_key: $meta->multiple_key
name: $meta->name
not_null: $meta->not_null
numeric: $meta->numeric
primary_key: $meta->primary_key
table: $meta->table
type: $meta->type
unique_key: $meta->unique_key
unsigned: $meta->unsigned
zerofill: $meta->zerofill
</pre>";
$i++;
}
mysql_free_result($result);
?>`

参见 mysql_field_seek()。

### 参数

`result`

  resource 型的结果集。此结果集来自对 mysql_query() 的调用。

`field_offset`
  The numerical field offset. If the field offset is not specified, the next field that was not yet retrieved by this function is retrieved. The `field_offset` starts at `0`.

### 返回值

Returns an object containing field information. The properties of the object are:

- name - column name
- table - name of the table the column belongs to
- max_length - maximum length of the column
- not_null - 1 if the column cannot be `null`
- primary_key - 1 if the column is a primary key
- unique_key - 1 if the column is a unique key
- multiple_key - 1 if the column is a non-unique key
- numeric - 1 if the column is numeric
- blob - 1 if the column is a BLOB
- type - the type of the column
- unsigned - 1 if the column is unsigned
- zerofill - 1 if the column is zero-filled

### 示例

示例 #2 mysql_fetch_field() example

`<?php
$conn = mysql_connect('localhost', 'mysql_user', 'mysql_password');
if (!$conn) {
die('Could not connect: ' . mysql_error());
}
mysql_select_db('database');
$result = mysql_query('select * from table');
if (!$result) {
die('Query failed: ' . mysql_error());
}
/* get column metadata */
$i = 0;
while ($i < mysql_num_fields($result)) {
echo "Information for column $i:<br />\n";
$meta = mysql_fetch_field($result, $i);
if (!$meta) {
echo "No information available<br />\n";
}
echo "<pre>
blob: $meta->blob
max_length: $meta->max_length
multiple_key: $meta->multiple_key
name: $meta->name
not_null: $meta->not_null
numeric: $meta->numeric
primary_key: $meta->primary_key
table: $meta->table
type: $meta->type
unique_key: $meta->unique_key
unsigned: $meta->unsigned
zerofill: $meta->zerofill
</pre>";
$i++;
}
mysql_free_result($result);
?>`

### 注释

> 注意: 此函数返回的字段名大小写敏感。

> 注意: If field or tablenames are aliased in the SQL query the aliased name will be returned. The original name can be retrieved for instance by using mysqli_result::fetch_field().

### 参见

- mysql_field_seek() - 将结果指针设置为指定的字段偏移量

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