利用PHP 简单实现加减法验证码

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<?php    header('Content-Type: image/png'); $im = imagecreatetruecolor( 200 , 50 );<br>//生成图片长宽    // Create some colors $white = imagecolorallocate($im, 255, 255, 255); $grey = imagecolorallocate($im, 128, 128, 128); $black = imagecolorallocate($im, 0, 0, 0);//背景色    imagefilledrectangle($im, 0, 0, 200, 49, $white);    // The text to draw $rand = rand( 1 ,2 ) ; $one = rand(1,9); $two = rand(1,9); if( $rand == 1 ){        $result = $one + $two;     $text = "$one+$two=?";    }else{     if( $one < $two ){         list( $two , $one ) = [ $one , $two ];     }     $result = $one - $two;     $text = "$one-$two=?"; }    session_start(); $_SESSION['code'] = $result; // Replace font $font = './Arvo-Regular.ttf';    //imageline( $im , 0 , rand( 1,49 ) , 199 , 30 , $grey ); //干扰线<br> // Add the text $i = 0; $len = strlen( $text ); while( $i < $len  ){     if( is_numeric( $text[$i] ) ){         imagettftext($im, 20, rand(-45,45), 20 * ($i+1) , 30, $black, $font, $text[$i]);     }else{         imagettftext($im, 20, 0 , 20 * ($i+1) , 30, $black, $font, $text[$i]);     } //echo $text[$i];     $i ++; } // Using imagepng() results in clearer text compared with imagejpeg() imagepng($im); imagedestroy($im);

　　如果生成图片为空，请检测字体引入路径是否有问题。