Show All Categories as Links in WordPress

You can use the function get_the_category_list() for this process.

<?php
$categories = get_the_category();
$separator = ' ';
$output = '';
if($categories){
	foreach($categories as $category) {
		$output .= '<a href="'.get_category_link( $category->term_id ).'" title="' . esc_attr( sprintf( __( "View all posts in %s" ), $category->name ) ) . '">'.$category->cat_name.'</a>'.$separator;
	}
echo trim($output, $separator);
}
?>

For more : http://codex.wordpress.org/Template_Tags/get_the_category

Get All Images From WordPress Media Gallery

Uploaded images are stored as posts with the type “attachment”. Use get_posts() and query for all attachments:

$args = array(
                'post_type' => 'attachment',
                'numberposts' => -1,
                'post_mime_type' =>'image',
                'post_status' => 'inherit',
                'post_parent' => null, // any parent
           );
$attachments = get_posts($args);
if ($attachments) {
    foreach ($attachments as $post) {
         setup_postdata($post);
         the_title();
         the_attachment_link($post->ID, false);
         the_excerpt();
     }
}

Now All images are displayed.

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create an autocomplete textbox in wordpress

Just add a div under the input tag

HTML Code:

<input type="text" id="city" name="city" autocomplete="off"/> 
<div id="key"></div>

replace the div after the success on you ajax.

Ajax Code:

     var ajaxurl="<?php echo admin_url( 'admin-ajax.php' ); ?>"; 
     var data ={ action: "city_action",  city:cid    };
        $.post(ajaxurl, data, function (response){
                     $('#key').html(response);
           });

PHP Code:

       function city_action_callback() {     
       global $wpdb;
            $city=$_GET['city'];
            $result =   $mytables=$wpdb->get_results("select * from ".$wpdb->prefix . "mycity where city like '%".$city."'" );   
            $data = "";
            echo '<ul>'
            foreach($result as $dis)
            {
                         echo '<li>'.$dis->city.'</li>';
            }
            echo '</ul>'    
         die();
       }

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Get category ID by using category name in wordpress

If you want to get category id by using category name then use the following code

function get_category_id($cat_name){
	$term = get_term_by('name', $cat_name, 'category');
	return $term->term_id;
}

then Just call the function with your category name as a parameter. for example

$category_ID = get_category_id('Books');

Now you can get the category Id in variable $category_ID.

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Get all user meta data by user ID in wordpress

If you want to get all user meta data by using id then use get_user_meta() function.

For example user id is 25. Use the following code for get all user meta data.

<?php
  $all_meta_for_user = get_user_meta( 25 );
  print_r( $all_meta_for_user );
?>

Results:

Array ( 
[first_name] => Array ( [0] => Tom ) 
[last_name] => Array ( [0] => Auger) 
[nickname] => Array ( [0] => tomauger ) 
[description] => etc.... )

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