how to replace string and preserve char cases in php

Question

i have file names strings like this : Admin_studies.php Studies_lang.php

and i want to replace it like this :

Admin_classes.php Classes_lang.php

which keep the case as it's and just replace the sting word

i tried something like this , but it will not keep the original chars cases

$newname = "classes";
$oldname = "studies";
$file_name = "Admin_studies.php";  //or may be $file_name = "Studies_lang.php";
echo preg_replace("/($oldname)/i","$1",$file_name );

Answer 1

You can set arrays for replacement templates

$newnames = ['classes', 'Classes'];
$oldnames = ['studies', 'Studies'];
$file_name = "Admin_Studies.php";
echo str_replace( $oldnames, $newnames, $file_name );