wordpress中输出验证码图片的有关问题

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<?php <br />
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    if(is_page('209')){<br />
        <br />
        header("Content-type: image/gif"); <br />
        header("Cache-Control: no-cache");<br />
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        $rands = rand(1000,9999); <br />
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        $im = imagecreate(40, 15); <br />
        //var_dump($im);exit();<br />
        imagecolorallocate($im, 240, 240, 240); <br />
        $loc = 2; <br />
        $color1=imagecolorallocate($im, 0, 0, 0); <br />
        for($i=0;$i<4;$i++){ <br />
            $color=imagecolorallocate($im, rand(0,255), rand(0,255), rand(0,255)); <br />
            imagestring($im, 4, ($loc+1), 1, substr($rands,$i,1), $color1); <br />
            imagestring($im, 4, $loc, 0, substr($rands,$i,1), $color); <br />
            $loc += 9; <br />
        } <br />
        imagegif($im); <br />
        imagedestroy($im);<br />
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        exit();<br />
    } //验证码<br />
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