直接将下面代码丢进functions.php即可

//Wordpress判断并自动添加图片ALT属性
function image_alt( $imgalt ){
global $post;
$title = $post->post_title;
$imgUrl = "<img\s[^>]*src=(\"??)([^\" >]*?)\\1[^>]*>";
if(preg_match_all("/$imgUrl/siU",$imgalt,$matches,PREG_SET_ORDER)){
if( !empty($matches) ){
for ($i=0; $i < count($matches); $i++){
$tag = $url = $matches[$i][0];
$judge = '/alt=/';
preg_match($judge,$tag,$match,PREG_OFFSET_CAPTURE);
if( count($match) < 1 ) $altURL = ' alt="'.$title.'" '; $url = rtrim($url,'>');
$url .= $altURL.'>';
$imgalt = str_replace($tag,$url,$imgalt);
}
}
}
return $imgalt;
}
add_filter( 'the_content','image_alt');