function addTextToImage( $text, $image_out )
{
    // ***** BEGIN CONFIGURATION ***** //

    // original image
    $filename = "template.gif";
    $width  = 150;
    $height = 150;

    // text position
    $left   = -1;   // -1 for horizontal center
    $top    = 50;  // -1 for vertical center

    // text font
    $ttf    = 'arial.ttf';
    $size   = 18;
    $angle  = 0;

    // text color
    $red    = 255;    // from 0 (black) to 255 (white)
    $green  = 255;    // from 0 (black) to 255 (white)
    $blue   = 255;    // from 0 (black) to 255 (white)

    // ***** END CONFIGURATION ***** //

    if( file_exists( $filename)) {

        $functions =    [".gif" => ["imagecreatefromgif", "imagegif"],
                         ".jpg" => ["imagecreatefromjpeg", "imagejpeg"],
                         ".jpeg" => ["imagecreatefromjpeg", "imagejpeg"],
                         ".png" => ["imagecreatefrompng", "imagepng"]
                        ];

        $pos = strrpos( $filename, "." );
        $ext = strtolower( substr( $filename, $pos ) );
        $func = $functions[$ext][0]; // get functionname
        $im = $func( $filename ); // function imagecreate...

        $col = ImageColorAllocate( $im, $red, $green, $blue ); // create color

        if( $left == -1 | $top == -1 ) { // horizontal or vertical center

            $box = imagettfbbox( $size, $angle, $ttf, $text ); // get box from text

            if( $left == -1 ) { // horizontal center
                $text_width = abs( $box[4] - $box[0] ); // top-right - bottom-left
                $left = round( ($width - $text_width ) / 2 ); // new value for left
            }

            if( $top == -1 ) { // vertical center
                $text_height = abs($box[5] - $box[1]);
                $top = round( ($height - $text_height) / 2 ) + $text_height; // new value for top
            }
        }

        Imagettftext( $im, $size, $angle, $left, $top, $col, $ttf, $text );

        $func = $functions[$ext][1]; // get functionname
        $func( $im, $image_out );   // function imagecreate...
    }
    else
        echo "file not exist!";
}