PHP Get file name starting with prefix

Question

This is a custom function. At the moment, this function get all the file in the default directory, strip \".php\" and list them.

The problem is that I want to only

Answer 1

 $target_file_png = glob($target_dir.'/group_'.$groupId.'*.png'); 

$target_file_png will return an array containing all the files in folder specified in the path $target_dir starting with '/group_'.$groupId.' and specify the file format as *.png