Differences between PHP PDOStatement objects bindpram of bindvalue of and bindcolumn

PDOStatement:: bindParam--Bind a parameter to the specified variable name.

Bind 1 PHP variable to the corresponding named placeholder or question mark placeholder in the SQL statement used as preprocessing. Unlike PDOStatement:: bindValue (), this variable is bound as a reference and takes its value only when PDOStatement:: execute () is called.

PDOStatement:: bindValue--Bind a value to a parameter.

Bind 1 value to the corresponding named placeholder or question mark placeholder in the SQL statement used as preprocessing.

<?php

$stm = $pdo->prepare("select * from users where user = :user");

$user = "jack";

// Correct 

$stm->bindParam(":user",$user);

// Errors 

$stm->bindParam(":user","jack");

// Correct 

$stm->bindValue(":user",$user);

// Correct 

$stm->bindValue(":user","jack");

 

// So use bindParam Is the first 2 Parameters can only use variable names, not variable values, and bindValue To you can use specific values. 

?>

PDOStatement:: bindColumn--Bind a column to an PHP variable.

Arranges a specific variable to bind to a given column in a query result set. Each call to PDOStatement:: fetch () or PDOStatement:: fetchAll () updates all variables bound to the column.

<?php

function  readData ( $dbh ) {

    $sql  =  'SELECT name, colour, calories FROM fruit' ;

    try {

        $stmt  =  $dbh -> prepare ( $sql );

        $stmt -> execute ();

 

        /*   Bind by column number   */

        $stmt -> bindColumn ( 1 ,  $name );

        $stmt -> bindColumn ( 2 ,  $colour );

 

        /*   Bind by column name   */

        $stmt -> bindColumn ( 'calories' ,  $cals );

 

        while ( $row  =  $stmt -> fetch ( PDO :: FETCH_BOUND )) {

            $data  =  $name  .  "\t"  .  $colour  .  "\t"  .  $cals  .  "\n" ;

            print  $data ;

        }

    }

    catch ( PDOException $e ) {

        print  $e -> getMessage ();

    }

}

readData ( $dbh );

?>