How to substitute a string for the value of a variable?

Question

PHP

There is a line _huge_it_small_gallery .
There is a variable that contains the full path to the image.
Example:
/uploads/2015/12/header3.jpg
Help me figure out how to make it so that it would turn out like this:
/uploads/2015/12/header3_huge_it_small_gallery.jpg
Here is my forych:

foreach ($query as $img) {
    $carouselItems .= '<li><a href="'.$img->image_url.'" class="carouselItem" rel="fancyboxCarousel'.$id.'"><img src="'.$img->image_url.'"></a></li>';
  }

Answer 1

<?php

foreach ($query as $img) {
  $img->image_url = str_replace(".jpg", "_huge_it_small_gallery.jpg", $img->image_url);
  $carouselItems .= '<li><a href="'.$img->image_url.'" class="carouselItem" rel="fancyboxCarousel'.$id.'"><img src="'.$img->image_url.'"></a></li>';
}

Answer 2

if you don't sweat
Either you cut the file resolution, shove between the line _huge_it_small_gallery and collect everything together
or regular expressions.

Answer 3

$p = '_huge_it_small_gallery';
$full = '/uploads/2015/12/header3'.$p.'.jpg';