Php registration code. how can this problem be solved?

Php registration code: the registration code of a website cannot be displayed. & nbsp; firefox & nbsp; see the following question & nbsp; (the server returns & nbsp; texthtml, & nbsp; php5.4) in the local environment & nbsp; change & nbsp; php & nbsp; to 5.3 & nbsp; to display the registration code. & Nbsp; the server returns & nbsp; imagejpeg below is the department debugging code to help analyze the php registration code
The registration code of a website cannot be displayed
In firefox, we can see the following problems (the server returns text/html, php5.4)

In the local environment, change php to 5.3 to display the registration code. The server returns image/jpeg

The following is the department debugging code. Why can't the verification code be properly displayed in php5.3 or later versions?

Session_register ("valicode ");
$ Width = 50; // define the length and width of the image first.
$ Height = isset ($ _ REQUEST ['height'])? $ _ REQUEST ['height']: 24;
$ Rand_str = "";
For ($ I = 0; $ I <4; $ I ++ ){
$ Rand_str. = chr (mt_rand (48, 57 ));
}
If (function_exists ("imagecreate ")){

Echo "fuction image create exists"; // added by stone on 20140724
$ _ SESSION ["valicode"] = strtolower ($ rand_str); // register a session

$ Img = imagecreate ($ width, $ height); // generate an image
Imagecolorallocate ($ img, 255,255,255); // image background color, ImageColorAllocate 1st definition color PHP considers it as background color
$ Black = imagecolorallocate ($ img, 127,157,185 );

For ($ I = 1; $ I <= 50; $ I ++) {// The Snowflake effect is displayed on the background.
Imagestring ($ img, 1, mt_rand (1, $ width), mt_rand (1, $ height), "#", imagecolorallocate ($ img, mt_rand (200,255 ), mt_rand (200,255), mt_rand (200,255 )));
}

For ($ I = 0; $ I <4; $ I ++) {// add text
Imagestring ($ img, mt_rand (2, 5), $ I * 10 + 6, mt_rand (2, 5), $ rand_str [$ I], imagecolorallocate ($ img, mt_rand (0,100 ), mt_rand (0,150), mt_rand (0,200 )));
}

Imagerectangle ($ img, $ width-1, $ height-1, $ black); // enclose the image with a black rectangle.

If (function_exists ("imagejpeg ")){
Ob_clean ();
Header ("content-type: image/jpeg \ r \ n"); imagejpeg ($ img );
} Else {
Ob_clean ();
Header ("content-type: image/png \ r \ n"); imagepng ($ img );
}

Imagedestroy ($ img );

} Else {
Echo "function image create NOT exists"; // added by stone on 20140724
$ _ SESSION ["valicode"] = "1234 ";
Ob_clean ();
Header ("content-type: image/jpeg \ r \ n ");
$ Fp = fopen ("./valicode.jpg", "r ");
Echo fread ($ fp, filesize ("./validate.jpg "));
Fclose ($ fp );
}

?>


------ Solution --------------------
Echo "fuction image create exists"; // added by stone on 20140724
Echo "function image create NOT exists"; // added by stone on 20140724
You can just remove the two sentences.