Split input string in PHP into multiple parts without breaking words

Question

have managed to take an input string and split it into two parts and write it to 2 files. What I want to achieve now is the be able to take it when it's bigger than my limit and split it into 3 or even 4 parts and write that data to separate files without breaking the input.

Here's what I have managed so far which I found here at this question: Split Strings in Half (Word-Aware) with PHP

public function createfiles(array $lines)
{
    $File1  = __DIR__ . '/file1.txt';
    $File2  = __DIR__ . '/file2.txt';

    $regexLines = [];

    foreach ($lines as $line) {
        $regexLines[] = preg_quote($line);
    }
    $data = implode('|', $regexLines);

    //current data input is 18000
    $myLimit = 10000;

    $dataLength = strlen($data);

    if ($dataLength > $myLimit) {

        $middle = strrpos(substr($data, 0, floor($dataLength / 2)), '/') + 1;
        //now want to split into four parts if input data is for instance 35000 characters

        // Strip off trailing /
        $data1 = substr($data, 0, $middle-1);
        $data2 = substr($data, $middle);
        //now want a $data3 and $data4 also stripping off a trailing /

        $this->writeToFile($File1, $data1);
        $this->writeToFile($File2, $data2);
        //now want to write to $File3 and $File4 if needed

    } else {
        $this->writeToFile($File1, $data);
    };
}

Answer 1

Finally found a solution after hours of digging and fiddling. I threw a big list at it and it broke it up nicely into 7 files for me without breaking words in half.

public function createmultiplefiles(array $lines)
{
    $regexLines = [];

    foreach ($lines as $line) {
        $regexLines[] = preg_quote($line);
    }
    $data = implode('|', $regexLines);

    $mylimit = 10000;
    $datalength = strlen($data);
    $lastpos = 0;

    for ($x = 1; $lastpos < $datalength; $x++) {

        if( ($datalength-$lastpos) >= $mylimit){
            $pipepos = strrpos(substr($data, $lastpos, $mylimit), '|');
            $splitdata = substr($data, $lastpos, $pipepos);
            $lastpos = $lastpos + $pipepos+1;
        }else{
            $splitdata = substr($data, $lastpos);
            $lastpos = $datalength;
        }
        $file = __DIR__ . 'myfile-' . $x . '.txt';
        $this->writeToFile($file, $splitdata);
    }
}