Php image verification code

Php verification code The code is as follows:

// File header...
Header ("Content-type: image/png ");
// Create white paper with true color
$ Im = @ imagecreatetruecolor (50, 20) or die ("image creation failed ");
// Obtain the background color
$ Background_color = imagecolorallocate ($ instant, 255,255,255 );
// Fill in the background color (this is similar to a barrel)
Imagefill ($ im, 0, 0, $ background_color );
// Obtain the border color
$ Border_color = imagecolorallocate ($ im, 200,200,200 );
// Draw a rectangle with a border color of 200,200,200
Imagerectangle ($ im, $ border_color );

// Show off the background line by line. use 1 or 0 in full screen.
For ($ I = 2; $ I <18; $ I ++ ){
// Obtain random light colors
$ Line_color = imagecolorallocate ($ im, rand (200,255), rand (200,255), rand (200,255 ));
// Draw a line
Imageline ($ im, 2, $ I, 47, $ I, $ line_color );
}

// Set the font size
$ Font_size = 12;

// Set the printed text
$ Str [0] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ ";
$ Str [1] = "abcdefghijklmnopqrstuvwxyz ";
$ Str [2] = "01234567891234567890123456 ";

// Obtain 1st random texts
$ Imstr [0] ["s"] = $ Str [rand (0, 2)] [rand (0, 25)];
$ Imstr [0] ["x"] = rand (2, 5 );
$ Imstr [0] ["y"] = rand (1, 4 );

// Obtain 2nd random texts
$ Imstr [1] ["s"] = $ Str [rand (0, 2)] [rand (0, 25)];
$ Imstr [1] ["x"] = $ imstr [0] ["x"] + $ font_size-1 + rand );
$ Imstr [1] ["y"] = rand (1, 3 );

// Obtain 3rd random texts
$ Imstr [2] ["s"] = $ Str [rand (0, 2)] [rand (0, 25)];
$ Imstr [2] ["x"] = $ imstr [1] ["x"] + $ font_size-1 + rand );
$ Imstr [2] ["y"] = rand (1, 4 );

// Obtain 4th random texts
$ Imstr [3] ["s"] = $ Str [rand (0, 2)] [rand (0, 25)];
$ Imstr [3] ["x"] = $ imstr [2] ["x"] + $ font_size-1 + rand );
$ Imstr [3] ["y"] = rand (1, 3 );

// Write random strings
For ($ I = 0; $ I <4; $ I ++ ){
// Obtain random darker colors
$ Text_color = imagecolorallocate ($ im, rand (50,180), rand (50,180), rand (50,180 ));
// Draw text
Imagechar ($ im, $ font_size, $ imstr [$ I] ["x"], $ imstr [$ I] ["y"], $ imstr [$ I] ["s"], $ text_color );
}

// Display the image
Imagepng ($ im );
// Destroy the image
Imagedestroy ($ im );
?>