Description:
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I try to bind param for string. But it doesn't work.

Test script:
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            $conn = new PDO('pgsql:host=localhost;dbname=base', 'login', 'pass');
            $stmt = $conn->prepare("select ST_Contains(ST_GeometryFromText('POLYGON((:downLeftPoint, :topLeftPoint, :topRightPoint, :downRightPoint, :downLeftPoint))'), POINT(100500,100500)::geometry)");
            $stmt->bindParam(':downLeftPoint', $coord['downLeftPoint']);
            $stmt->bindParam(':topLeftPoint', $coord['topLeftPoint']);
            $stmt->bindParam(':topRightPoint', $coord['topRightPoint']);
            $stmt->bindParam(':downRightPoint', $coord['downRightPoint']);
            $stmt->bindParam(':downLeftPoint', $coord['downLeftPoint']);
            $stmt->execute();

Expected result:
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SQL query:

select ST_Contains(ST_GeometryFromText('POLYGON((100500 100500, 200500 200500, 300500 300500, 400500 400500, 100500 100500))'), POINT(100500,100500)::geometry)

Actual result:
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Error: PDOStatement::bindParam(): SQLSTATE[HY093]: Invalid parameter number: :downLeftPoint