PHP中的bindParam覆盖错误 [英] Error with bindParam overwriting in PHP

问题描述

这有点奇怪，我很可能会编写完全错误的代码-因此，为什么我在两天内在脚本的完全不同的部分中两次遇到相同的错误.我正在使用的代码如下:

This is a bit of a weird one, and I could well be coding this completely wrong - hence why I've hit the same error twice in two days, in completely different parts of a script. The code I'm using is below:

    public function findAll( $constraints = array() ) {

        // Select all records
        $SQL = 'SELECT * FROM ' . $this->tableName;

        // See if there's any constraints
        if( count( $constraints ) > 0 ) {
            $SQL .= ' WHERE ';

            foreach( $constraints as $field => $value ) {
                $SQL .= $field . ' = :' . $field . ' AND ';
            }

        }

        // Remove the final AND and prepare the statement
        $SQL = substr( $SQL, 0, -5 );       
        $PDOStatement = $this->PDO->prepare( $SQL );

        // Loop through constraints and bind parameters
        foreach( $constraints as $field => $value ) {
            print 'Binding ' . $field . ' to ' . $value . ' 
';
            $PDOStatement->bindParam( $field, $value );
        }

        $PDOStatement->execute();
        var_dump($PDOStatement);        

        while ( $results = $PDOStatement->fetch( PDO::FETCH_ASSOC ) ) {

            var_dump($results);

        }

    }

我对使用PDO很陌生，但基本上我正尝试传递一系列约束，例如

I'm pretty new to using PDO, but basically I'm attempting to pass an array of constraints e.g.

array( 'active' => 1, 'name' => 'James' )

并返回表

WHERE active = 1 AND name = 'James'

如果我使用此数组，则从第一个

If I use this array, the SQL executed from the first

var_dump( )

执行的SQL是

SELECT * FROM {table} WHERE active = :active AND name = 'James'

-完全符合我的期望.绑定参数将完全按预期打印活动绑定到1"和将名称绑定到James".这些行存在于数据库中，但是对$ results的第二个

- exactly as I expect. The bound parameters prints 'Binding active to 1' and 'Binding name to James' - exactly as expected. The rows exist in the database, and yet the second

var_dump()

调用什么也不输出-即，没有返回行.

call for $results outputs nothing - i.e. no rows are returned.

如果我传递一个单一约束的数组，例如

If I pass an array of a single constraint, e.g.

array( 'active' => 1 )

，这很好用.似乎是在多个约束都通过的情况下，它才停止工作.

, this works perfectly fine. It appears to be whenever multiple constraints are passed that it stops working.

推荐答案

这是因为 bindParam 通过绑定到变量来工作，并且您正在将变量($value)重用于多个值.尝试使用 bindValue .

That's because bindParam works by binding to a variable, and you are re-using the variable ($value) for multiple values. Try with bindValue instead.

甚至更好；而是将值作为数组传递给 execute .这使该语句变为无状态，这在编程中通常是一件好事.

Or even better yet; Pass the values as an array to execute instead. This makes the statement stateless, which is generally a good thing in programming.

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