Executing PDO Query changes bound parameter from integer to string

Question

Code Sample

$query = $this->db->prepare( $sql );                  // prepare sql
$query->bindParam( 'start', $start, PDO::PARAM_INT ); // bind start
$query->bindParam( 'end', $end, PDO::PARAM_INT );     // bind end
$query->bindParam( 'language', $this->language );     // bind language
$query->bindValue( 'keyword', "%$keyword%" );         // bind keyword

var_dump( $end );
$query->execute();
var_dump( $end );

Output

int 2
string '2' (length=1)

But... if I switch the order of binds...

$query = $this->db->prepare( $sql );                  // prepare sql
$query->bindParam( 'language', $this->language );     // bind language
$query->bindValue( 'keyword', "%$keyword%" );         // bind keyword
$query->bindParam( 'start', $start, PDO::PARAM_INT ); // bind start
$query->bindParam( 'end', $end, PDO::PARAM_INT );     // bind end

var_dump( $end );
$query->execute();
var_dump( $end );

Output

int 2
int 2

PHP Version: 5.3.8 on Windows

Can anyone explain why this is happening?

Answer 1

Try turning of emulation for preparing statements

$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);

Answer 2

Checked this with PHP 5.3.13 - two versions of your code gives me:

int 2
string '2' (length=1)

Additionally, with using bindValue() instead of bindParam() two versions of code gives me:

int 2
int 2

p.s. I prefer work with bindValue() and not mix it with bindParam(). Using bindParam() doesn't gives any performance improvements. Some people thinks that passing by values and passing by pointer in PHP works as in C/C++, but this is wrong thinking. Using bindParam() may lead to bugs that hard to find them when they occurs.