How to get current category

Question

Hello I'm in a bit of a trouble. I don't know what's wrong with what I'm doing. I want to add class to current category. So my php looks like this:

    <menu id="nav">
        <ul>   
            <?php $cat_id = get_cat_ID();
            foreach( $categories as $c ):?>         
            <li class="<?php if(($c->term_id) == $cat_id){echo 'active' ;} ?>">
            <a href="<?php echo get_category_link( $c->term_id ); ?>" title="<?php echo $c->cat_name ;?>">
            <?php echo $c->cat_name ;?>
            </a>                
            </li>
        <?php endforeach;   ?>  
        </ul>
</menu>

I just want to add active class to the current category. But this is not working.

Answer 1

You can use get_queried_object(), which will return category object.

See documentation:

https://codex.wordpress.org/Function_Reference/get_queried_object

Answer 2

Put your $c term (in your loop) in a print_r/var_dump to see if the property you are trying to compare the values of is of the actual value that you are looking for (See below).

I've also added a ternary operator in the place of your if statement, it is just better practice. (Read below for more on ternary operators).

<menu id="nav">
    <ul>   
    <?php $cat_id = get_cat_ID();
    foreach( $categories as $c ):?>
        <?php print_r($c); ?>         
        <li class="<?php echo $c->term_id == $cat_id ? 'active' : null ;} ?>">
        <a href="<?php echo get_category_link( $c->term_id ); ?>" title="<?php echo $c->cat_name ;?>">
        <?php echo $c->cat_name ;?>
        </a>                
        </li>
    <?php endforeach;   ?>  
    </ul>
</menu>

Ternary Operator

In computer programming, ?: is a ternary operator that is part of the syntax for a basic conditional expression in several programming languages. It is commonly referred to as the conditional operator, inline if (iif), or ternary if.

if(1==1) echo 'true'; 
else echo 'false';

can be done in a ternary operator like so:

echo 1==1 ? 'true' : 'false';

Another example

if(1==1) $boolean = true;
else $boolean = false;

can be done in a ternary operator like so:

$boolean = 1==1 ? true : false;

Since PHP 5.3, the 'middle part' of the operator can be left out. Shorthand ternary operators can be used to match only false

if(1!=2) echo 'false';

The ternary operator:

echo 1!=2 ?: 'false';

Read more: http://php.net/manual/en/language.operators.comparison.php