<?php $the_query = new WP_Query( 'page_id=46' ); ?>
<?php while ($the_query -> have_posts()) : $the_query -> the_post();  ?>
<?php the_excerpt(); ?>
<?php endwhile;?>

<?php
the_excerpt_max_charlength(140);

function the_excerpt_max_charlength($charlength) {
	$excerpt = get_the_excerpt();
	$charlength++;

	if ( mb_strlen( $excerpt ) > $charlength ) {
		$subex = mb_substr( $excerpt, 0, $charlength - 5 );
		$exwords = explode( ' ', $subex );
		$excut = - ( mb_strlen( $exwords[ count( $exwords ) - 1 ] ) );
		if ( $excut < 0 ) {
			echo mb_substr( $subex, 0, $excut );
		} else {
			echo $subex;
		}
		echo '[...]';
	} else {
		echo $excerpt;
	}
}
?>

เอามารวมกัน

<?php $the_query = new WP_Query( 'page_id=46' ); ?>
<?php while ($the_query -> have_posts()) : $the_query -> the_post();  ?>
// เอาอันนี้ออก <?php the_excerpt(); ?>
<?php endwhile;?>

<?php
the_excerpt_max_charlength(140);

function the_excerpt_max_charlength($charlength) {
	$excerpt = get_the_excerpt();
	$charlength++;

	if ( mb_strlen( $excerpt ) > $charlength ) {
		$subex = mb_substr( $excerpt, 0, $charlength - 5 );
		$exwords = explode( ' ', $subex );
		$excut = - ( mb_strlen( $exwords[ count( $exwords ) - 1 ] ) );
		if ( $excut < 0 ) {
			echo mb_substr( $subex, 0, $excut );
		} else {
			echo $subex;
		}
		echo '[...]';
	} else {
		echo $excerpt;
	}
}
?>

หรือ
ใน functions.php

function excerpt($limit) {
      $excerpt = explode(' ', get_the_excerpt(), $limit);

      if (count($excerpt) >= $limit) {
          array_pop($excerpt);
          $excerpt = implode(" ", $excerpt) . '...';
      } else {
          $excerpt = implode(" ", $excerpt);
      }

      $excerpt = preg_replace('`\[[^\]]*\]`', '', $excerpt);

      return $excerpt;
}

function content($limit) {
    $content = explode(' ', get_the_content(), $limit);

    if (count($content) >= $limit) {
        array_pop($content);
        $content = implode(" ", $content) . '...';
    } else {
        $content = implode(" ", $content);
    }

    $content = preg_replace('/\[.+\]/','', $content);
    $content = apply_filters('the_content', $content); 
    $content = str_replace(']]>', ']]>', $content);

    return $content;
}

นำไปใช้

<?php echo excerpt(25); ?>

ตัวอย่าง หน้าที่นำไปใช้ (โค๊ดนี้ดึงหน้า page ที่ต้องการ แล้ว กำหนดขนาดความยาวข้อความ)

<?php $the_query = new WP_Query( 'page_id=46' ); ?>
<?php while ($the_query -> have_posts()) : $the_query -> the_post();  ?>
<?php echo excerpt(25); ?>
<?php endwhile;?>