How to change class of first echo result in PHP?

Question

Easy one, but I can't find an answer.

I wanna to list sub-categories to create tabs in code below. This one works fine in my output. But the first tab needs a <li class= "selected" > to show the content on page load .

How to force the first echo result to include a class on <li> element ?

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[ Output ]

Actual: .......... Category 1 | Category 2 | Category 3

Needed: .......... Category 1* | Category 2 | Category 3

*class="selected"

  <ul class="cd-tabs-navigation">

  <?php
  $argumentos = array(
  'hide_empty' => 1,
  'child_of' => 44,
  );
  $categories = get_categories($argumentos);
  foreach($categories as $category) {
  echo '<li><a data-content="' . $category->slug . '" href="#' . $category->slug . '">' . $category->name . '</a></li>';
  }
  ?>

  </ul>

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[ EDIT ]

The solution by Lal. Thank you everyone!

  foreach($categories as $category) {
  if(++$i==1)
  echo '<li class="selected"><a class="selected" data-content="' . $category->slug . '" href="#' . $category->slug . '">' . $category->name . '</a></li>';
  else
  echo '<li><a data-content="' . $category->slug . '" href="#' . $category->slug . '">' . $category->name . '</a></li>';
  }

Answer 1

I would suggest you to use a counter.. Not sure if this is the right way to do it..

Change your foreach as follows

$i=0;
foreach($categories as $category) {
  if($i==0)
    echo '<li class="selected"><a data-content="' . $category->slug . '" href="#' . $category->slug . '">' . $category->name . '</a></li>';
  else
    echo '<li><a data-content="' . $category->slug . '" href="#' . $category->slug . '">' . $category->name . '</a></li>';
  $i++;
  }

OR

As suggested in the answer here, you could use array_shift() to process the first item in the array separatley.

That is, do it as below

$first = array_shift($categories);
echo '<li class="selected"><a data-content="' . $first ->slug . '" href="#' . $first ->slug . '">' . $first ->name . '</a></li>';
foreach($categories as $category) {
  echo '<li><a data-content="' . $category->slug . '" href="#' . $category->slug . '">' . $category->name . '</a></li>';
}

Read more about array_shift() in the docs