Rename files while uploading with php - php

Question

I have a html form + php for uploading 3 pdfs similarly. while uploading i have to cut the names of the files. For instance instead of AB_2020_02_02.pdf i want to have it changed in AB.pdf - for all three files simultaneously. I tried with rename($original_filename, substr($original_filename, 2) . '.pdf'); Any other ideas?
This is the entire code:
<?php
// Set Upload Path
$target_dir = '';
$_FILES = substr($_FILES, 2, strlen($_FILES) - 12);
if( isset($_FILES['fileUpload']['name'])) {
$total_files = count($_FILES['fileUpload']['name']);
for($key = 0; $key < $total_files; $key++) {
// Check if file is selected
if(isset($_FILES['fileUpload']['name'][$key])
&& $_FILES['fileUpload']['size'][$key] > 0) {
$original_filename = $_FILES['fileUpload']['name'][$key];
rename($original_filename, substr($original_filename, 2) . '.pdf');
$target = $target_dir . basename($original_filename);
$tmp = $_FILES['fileUpload']['tmp_name'][$key];
move_uploaded_file($tmp, $target);
}
}
}
?>

Answer 1

$target_dir = '';
if( isset($_FILES['fileUpload']['name'])) {
$total_files = count($_FILES['fileUpload']['name']);
for($key = 0; $key < $total_files; $key++) {
// Check if file is selected
if(isset($_FILES['fileUpload']['name'][$key])
&& $_FILES['fileUpload']['size'][$key] > 0) {
$original_filename = $_FILES['fileUpload']['name'][$key];
$rename = explode('_',$original_filename);
$target = $target_dir . $rename[0].".pdf";
$tmp = $_FILES['fileUpload']['tmp_name'][$key];
move_uploaded_file($tmp, $target);
}
}
}

Answer 2

Rename directly in move_uploaded_file(...)
<?php
// Set Upload Path
$target_dir = '';
$_FILES = substr($_FILES, 2, strlen($_FILES) - 12);
if( isset($_FILES['fileUpload']['name'])) {
$total_files = count($_FILES['fileUpload']['name']);
for($key = 0; $key < $total_files; $key++) {
// Check if file is selected
if(isset($_FILES['fileUpload']['name'][$key])
&& $_FILES['fileUpload']['size'][$key] > 0) {
$original_filename = $_FILES['fileUpload']['name'][$key];
$target = $target_dir . substr($original_filename, 2).'.pdf' ;
$tmp = $_FILES['fileUpload']['tmp_name'][$key];
move_uploaded_file($tmp, $target);
}
}
}
?>