Extending PDO Statement Class

You can set the class with PDO::setAttribute():

PDO::ATTR_STATEMENT_CLASS: Set user-supplied statement class derived from PDOStatement. Cannot be used with persistent PDO instances. Requires array(string classname, array(mixed constructor_args)).

Example:

$pdo->setAttribute(PDO::ATTR_STATEMENT_CLASS, [Custom::class]);

This is answered by a user in the PHP Manual under PDO:

class Database extends PDO {
    function __construct($dsn, $username="", $password="", $driver_options=array()) {
        parent::__construct($dsn,$username,$password, $driver_options);
        $this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('DBStatement', array($this)));
    }
}
class DBStatement extends PDOStatement {
    public $dbh;
    protected function __construct($dbh) {
        $this->dbh = $dbh;
    }
}

You can find his original answer by searching: 'smileaf' at this page: https://php.net/manual/en/book.pdo.php

This is my code to save the result of a select query into a text file as insert statement. I first extend the PDOStatement class to add the custom method saveResultAsInsertStatement:

<?php
class MyPDOStatement extends PDOStatement {
    protected $pdo;

    protected function __construct($pdo) {
        $this->pdo = $pdo;
    }
    public function saveResultAsInsertStatement($filename) {
        $result = '';
        $columnData = $this->fetchAll(PDO::FETCH_ASSOC);
        if ($columnData != null) {
            $fieldCount = count($columnData[0]);
            $rowsCount = count($columnData);
            $columnsName = array_keys($columnData[0]);
            $result = "INSERT INTO %s ( \n";
            $result .= join(",\n", $columnsName);
            $result .= ") VALUES\n";
            $r = 0;
            foreach ($columnData as $row) {
                $result .= "(";
                $c = 0;
                foreach ($row as $key => $field) {
                    $result .= $this->pdo->quote($field);
                    $result .= ( ++$c < $fieldCount) ? ', ' : '';
                }
                $result .= ")";
                $result .= ( ++$r < $rowsCount) ? ',' : '';
                $result .= "\n";
            }
        }

        $f = fopen($filename, "w");
        fwrite($f, $result);
        fclose($f);
    }

}
?>

Then I extend the PDO class to set the attribute PDO::ATTR_STATEMENT_CLASS

<?php
class MyPDO extends PDO {
    public function __construct(... PDO constructor parameters here ... ) {
        parent::__construct( ... PDO construct parameters here ...);
        $this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('MyPDOStatement', array($this)));
    }

}
?>

So then, I can write:

<?php
$conn = new MyPDO(... PDO constructor parameters here ...);

$sql = ... your select statement here...

$conn->query($sql)->saveResultAsInsertStatement(... name of the file here ...);


?>