Break lines on two equal parts not breaking whole words

_break_lines.php

<?php

// Check if the input file exists
$inputFile = "_input_file_name.txt";


// Function to break a line into two parts, aiming for equal number of characters, without breaking words
function breakLineEqually($line) {
    $length = strlen($line);
    $mid = intdiv($length, 2);

    $spaceBefore = strrpos($line, ' ', $mid - $length);
    $spaceAfter = strpos($line, ' ', $mid);

    if ($spaceBefore === false && $spaceAfter === false) {
        // No spaces in the string
        return [$line, ''];
    }

    if ($spaceBefore === false) {
        $breakPoint = $spaceAfter;
    } elseif ($spaceAfter === false) {
        $breakPoint = $spaceBefore;
    } else {
        // Choose the closest space to the middle
        $breakPoint = ($mid - $spaceBefore < $spaceAfter - $mid) ? $spaceBefore : $spaceAfter;
    }

    $part1 = trim(substr($line, 0, $breakPoint));
    $part2 = trim(substr($line, $breakPoint));

    return [$part1, $part2];
}

if (!file_exists($inputFile)) {
    echo "The file input.txt does not exist.\n";
    exit(1);
}

// Read the file line by line
$lines = file($inputFile, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
if ($lines === false) {
    echo "An error occurred while reading the file.\n";
    exit(1);
}

// Process each line
foreach ($lines as $line) {
    list($part1, $part2) = breakLineEqually($line);
    echo $part1 . "\t" . $part2 . "\n";
}