Cut the file name taking advantage of their title pattern.

rename.php

<?php
class FileUtils
{
    public $keyword;
    public $filenames;
    public $extension;
    public $folder;
    public $newFile;
	public $is_left;

    function __construct()
    {
        $this->keyword = '';
        $this->filenames = [];
        $this->extension = 'php';
        $this->folder = '.';
        $this->newFile = [];
		$this->is_left = true; // left to right
    }

    function setFolder($folder)
    {
        $this->folder = $folder;
    }

    function getFolder()
    {
        return $this->folder;
    }

    function setExtension($extension)
    {
        $this->extension = $extension;
    }

    function getActiveExtension()
    {
        return $this->extension;
    }

    function setKeyword($keyword)
    {
        $this->keyword = $keyword;
    }

    function getKeyword()
    {
        return $this->keyword;
    }

    function insertDot()
    {
	// 
    }

    function getExtension($filename)
    {
        return substr($filename, strlen($filename)-3, 3);
    }

    function longerThan($filename) {
        $lengthMinusExtension = strlen($filename)-3;
        if ($lengthMinusExtension <= strlen($this->keyword)) {
            return false;
        } else {
            return true;
        }
    }

    function isMatch($filename)
    {
        if (substr($filename, 0, strlen($this->keyword)) == $this->keyword) {
            return true;
        } else {
            return false;
        }
    }

    function getNewName($filename)
    {
        $panjangKeyword = strlen($this->keyword);
        $panjangNamaFile = strlen($filename);

        return substr($filename, $panjangKeyword, $panjangNamaFile);
    }

    function hasString($source, $str, $pos)
    {
        if (substr($source, $pos, strlen($str)) == $str) {
            return true;
        } else {
            return false;
        }
    }

    function printNewFilenames()
    {
        foreach($this->newFilenames as $key => $filename) {
            echo $filename . "\n";
        }
    }

    function insertString($str, $pos)
    {

        $arrFilenames = [];
        foreach($this->filenames as $key => $filename) {
            $leftSide  = substr($filename, 0, $pos-1);
            $rightSide = substr($filename, $pos, strlen($filename));
            $newFile   = $leftSide . $str . $rightSide;

            if ($newFile != $filename) {
                $oldFilePath = $this->folder . '/' . $filename;
                $newFilePath = $this->folder . '/' . $newFile;
                if (rename($oldFilePath, $newFilePath))
                {
                    $arrFilenames[] = $newFile;
                }
            }
        }
        $this->newFilenames = $arrFilenames;
    }

    function renameCutFilenames($moveNumbering=false)
    {
        $arrFilenames = [];
        foreach($this->filenames as $key => $filename) {
            if ($this->isMatch($filename)) {
                if ($moveNumbering == true) {
                    $arr = explode('#', $filename);
                    $filename = trim($arr[1]) . ' ' . trim($arr[0]);  
                }

                $oldFile = $this->folder . '/' . $filename;
                $newFile = $this->folder . '/' . $this->getNewName($filename);
                if (rename($oldFile, $newFile)) {
                    $arrFilenames[] = $this->getNewName($filename);
                }
            }
        }
        $this->newFilenames = $arrFilenames;
    }

    function getFiles()
    {
        if ($handle = opendir($this->folder)) {
            $arrFiles = [];
            while (false !== ($entry = readdir($handle))) {
                if ($entry != "." && $entry != ".." && !is_dir($entry) && $this->getExtension($entry)==$this->extension) {
                    $arrFiles[] = $entry;
                }
            }
            closedir($handle);
            $this->filenames = $arrFiles;
        } else {
            $this->filenames = [];
        }
    }
}


$fileUtils = new FileUtils();

// file name extension
$extension = 'mp4';
$fileUtils->setExtension($extension);

// string to be cut from the file name
$keyword = 'ReactJS Tutorial - ';
$fileUtils->setKeyword($keyword);

// target folder
$folder = 'D:/learn/reactjs/codevolution';
$fileUtils->setFolder($folder);

$files = $fileUtils->getFiles();
$fileUtils->renameCutFilenames();