用到一个开源库：

https://imagettftextblur.agjgd.org/examples/shadow/

github地址：https://github.com/andrewgjohnson/imagettftextblur

使用示例：

//引入文字发光

include __ROOTDIR__."libs/imagettftextblur/imagettftextblur.php";



// 背景颜色

$text_color = imagecolorallocate($im, 216, 227, 231);

$shadow_color = imagecolorallocate($im, 57, 47, 65);



//定义x轴在字体上增加的大小

            $xleft=6;

            foreach ($str as $k=>$v){



                if ($type=='1'){

                    //imagettftext($im, $size, 0, ($width-mb_strlen($v)*($size+$xleft))/2, ($height-$k*($size+56))/2+(count($str)*10), $text_color, $font, $v);

                    $x_offset=($width-mb_strlen($v)*($size+$xleft))/2;

                    $y_offset=($height-$k*($size+56))/2+(count($str)*10);

                }else{

                    //imagettftext($im, $size, 0, ($width-mb_strlen($v)*($size+$xleft))/2, ($height-$k*($size+36))/2+(count($str)*12), $text_color, $font, $v);

                    $x_offset=($width-mb_strlen($v)*($size+$xleft))/2;

                    $y_offset=($height-$k*($size+36))/2+(count($str)*12);

                }

                // place the shadow onto our image

                imagettftextblur($im, $size, 0, $x_offset + 5, $y_offset + 5, $shadow_color, $font,$v, 10);

                // place the text onto our image

                imagettftextblur($im, $size, 0, $x_offset, $y_offset, $text_color, $font, $v);

            }