- substr: documentation ( source)
- strpos: documentation ( source)
- strrpos: documentation ( source)
<?php
$str = "blur/blur/myPhotoName_20170818_111453.jpg";
$pos = strrpos($str, "/")+1;
$str = substr($str, $pos, strpos($str, "_")-$pos) . substr($str, strpos($str, "."));
Echo $str;