Pass form values to WordPress query_posts(category name / category id) function to retrieve posts from a specific category

I was taking a look at WordPress Support Forum and found this doubt, about how to pass form values to the query_posts function to retrieve posts from a specific category.
Eu etava dando uma olhada no Forum de Suporte WordPress e achei esta dúvida, sobre como passar valores de formulários para a função query_posts, para retornar posts de uma categoria específica.

First of all, there’s a difference between working with the category name and the category id as parameters:
Primeiramente, há uma diferença entre trabalhar com o nome da categoria e o id da categoria como parâmetros:

//working with the category name
$catnam = $_GET["catnam"]; // or $_POST["catnam"]; // using GET or POST depends on your form submit method
query_posts("category_name=$catnam");

//working with the category id
$catid = $_GET["catid"]; // or $_POST["catid"]; //using GET or POST depends on your form submit method
query_posts("cat=$catid");

Well, now let’s see the complete code.
Bem, agora vamos ver o código completo.

<?
//category name or id
$catid = $_GET["catid"];

// passing the parameters to query_posts
query_posts("cat=$catid");

if (have_posts()) :
     while (have_posts()) : the_post();				 	
?>
     <div>
       <h3><a href="<?php the_permalink();?>"><?=get_the_title();?></a></h3>
     </div>
     <div>
       <p><?=get_the_content();?></p>
     </div>
<?
    endwhile;     
else:
?>
     <div>
       <p>No registers found.</p>								
     </div>
<?
endif;
?> 

Maybe you will enjoy taking a look on another post, where I talk about page navigation on Category Pages.
Talvez você curta dar uma olhada em outro post, onde eu falo sobre navegação de página em Páginas de Categoria.

Get the first image from wordpress posts(content)

There’s a lot of ways to get the first image from wordpress posts.

I’ve found a workaround, using the function bellow. Just Put it on your “functions.php” file.

function get_first_image($content,$wdt,$hgt) {
	$first_img = '';
	$output = preg_match_all('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i', $content, $matches);
	$pref_img = $matches [1] [0];

	if(empty($pref_img)){ //Defines a default image
		$pref_img = "";
	}
	else{
		$posgif = strrpos($pref_img , ".gif", 0);
		if($posgif > 0){
			$iext = "gif";
			$posimg = $posgif;
		}
		$posjpg = strrpos($pref_img , ".jpg", 0);
		if($posjpg > 0){
			$iext = "jpg";
			$posimg = $posjpg;
		}
		$posjpeg = strrpos($pref_img , ".jpeg", 0);
		if($posjpeg > 0){
			$iext = "jpeg";
			$posimg = $posjpeg;
		}
		$pospng = strrpos($pref_img , ".png", 0);
		if($pospng > 0){
			$iext = "png";
			$posimg = $pospng;
		}
		$first_img = substr($pref_img, 0, $posimg).".".$iext."?w=".$wdt."&h=".$hgt;
	}	
	return $first_img;
}

Call it in your code, like this:

<img src="<?php echo get_first_image_mat(get_the_content(),230,138);?>" border="0" style="width:230px;height:138px">

Remove first image from a wordpress post(the_content)

So tired… soul searching… I was looking for a solution to remove the first image from wordpress posts. I’ve found some, but they didn’t work. So, I decided to make my own code:

Just put it on your “functions.php” file.

function clear_first_image($content) {
	/*
		Warning:
		# I know light sabers are better...
			...but maybe I'm not good enough, so I use laser guns :)
		# It is not an elegant solution, but it works
		# Maybe someday I'll change it to use more regular expressions than logic
		# It's not recommended use this solution when you are
		processing large amount of data, like when you are on a loop
		# To call it on your code, under a loop(like "while" or "for"), use:
			echo clear_first_image(get_the_content())

		# Good luck! May the force be with you!
		alvaron8@gmail.com
	*/
	// checks if there is a first image
	$postst = strpos($content, '<img');
	if($postst !== false):
		// #letz check if the image has a link and remove it
		$output = preg_match_all('/<a.+href=[\'"]([^\'"]+)[\'"].*><img.+src/i', $content, $matches);
		$link_img = $matches [1] [0];
		if($link_img!=""):
			// we get the first link 'begin' tag
			$lnkini = strpos($content , '<a href', 0);
			// then we get the first link 'close' tag
			$lnkend = strpos($content, '<img', $lnkini);
			// letz get the hole first link tag now
			$replnk = substr($content, $lnkini, ($lnkend-$lnkini));
			// now we replace the first link tag in the content
			$tmpctd = preg_replace("'".$replnk."'",'',$content);
			// letz clear the link tag close
			$lnkcld = strpos($content , '</a>', 0);
			$content = substr($tmpctd, 0, $lnkcld).substr($tmpctd, $lnkcld, strlen($tmpctd));
		endif;
		// #removing the first image
			// we get the first image 'open' tag
			$posini = strpos($content , '<img', 0);
			// then we get the first image 'close' tag
			$posend = strpos($content, '>', $posini);
			// letz get the hole first image tag now
			$repimg = substr($content, $posini, ($posend-$posini)+1);
			// now we replace the first image tag in the content
			$postOutput = preg_replace("'".$repimg."'",'',$content);
	else:
		$postOutput=$content;
	endif;
	return $postOutput;
}

And call it on your code, like this:

echo clear_first_image(get_the_content());