how to parse a string for seperate font effects for First / Remaining letters?

good evening,

i am looking for a method to parse a string, to facilitate different text decoration for the first letter and the remaining letters of that string.

currently i am using the following code to extract the text name for categories on a given post :

<?php $category = get_the_category(); $firstCategory = $category[0]->cat_name; echo $firstCategory;?>

is there a way to parse $firstCategory into separate strings for the first letter and remaining letters?

hoping to be able to implement something like :

<span class="h1"> <?php echo $firstCatfirstLetter;?></span>
<span class="standard> <?php echo $firstCatRemaining;?></span>