php imagettftext 规定宽度内自动换行

function draw_txt_to($card,$pos,$string){ $font_color = imagecolorallocate($card, $pos['color'][0],$pos['color'][1],$pos['color'][2]);$font_file = BASEPATH.'../'.cfg('ttf');$_string='';$__string='';for($i=0;$i<mb_strlen($string);$i++){$box=imagettfbbox($pos['fontsize'],0,$font_file,$_string);$_string_length=$box[2]-$box[0];$box=imagettfbbox($pos['fontsize'],0,$font_file,mb_substr($string,$i,1));if( $_string_length+$box[2]-$box[0]<$pos['width']){$_string.=mb_substr($string,$i,1);}else{$__string.=$_string."\n";$_string=mb_substr($string,$i,1);}}$__string.=$_string; $box=imagettfbbox($pos['fontsize'],0,$font_file,mb_substr($__string,0,1));imagettftext($card,$pos['fontsize'],0,$pos['left'],$pos['top']+($box[3]-$box[7]),$font_color,$font_file,$__string);}