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# PDOStatement::columnCount

(no version information, might be only in CVS)

PDOStatement::columnCount -- Returns the number of columns in the result set

## 说明

int PDOStatement::columnCount ( void )

警告
本函数是实验性的。本函数的行为，包括函数名称以及其它任何关于本函数的文档可能会在没有通知的情况下随 PHP 以后的发布而改变。使用本函数风险自担。

Use PDOStatement::columnCount() to return the number of columns in the result set represented by the PDOStatement object.

If the PDOStatement object was returned from PDO::query(), the column count is immediately available.

If the PDOStatement object was returned from PDO::prepare(), an accurate column count will not be available until you invoke PDOStatement::execute().

## 返回值

Returns the number of columns in the result set represented by the PDOStatement object. If there is no result set, PDOStatement::columnCount() returns 0.

## 例

例子 1. Counting columns

This example demonstrates how PDOStatement::columnCount() operates with and without a result set.

`<?php
$dbh = new PDO('odbc:sample', 'db2inst1', 'ibmdb2');
$sth = $dbh->prepare("SELECT name, colour FROM fruit");
/* Count the number of columns in the (non-existent) result set */
$colcount = $sth->columnCount();
print("Before execute(), result set has $colcount columns (should be 0)\n");
$sth->execute();
/* Count the number of columns in the result set */
$colcount = $sth->columnCount();
print("After execute(), result set has $colcount columns (should be 2)\n");
?>`

上例将输出：

    Before execute(), result set has 0 columns (should be 0)
    After execute(), result set has 2 columns (should be 2)

## 参见

PDO::prepare()
PDOStatement::execute()
PDOStatement::rowCount()

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PDOStatement::bindParam | 上一级 | PDOStatement::errorCode