Generates random names and puts them in a .txt file

nameGenerator.php

<?php
//Generates random names and puts them in a txt file

$fileName = 'nameDatabase.txt';
$mode = 2;                  //MODE 1: array of names || MODE 2: one name per line
$amountOfNames = 100;       //Amount of names to be generated
$startTime = microtime(true); //Starts timer
$adjs = array(
    'Impressive',
    'Overwhelming',
    'Crushing',
    'Powerful',
    'Great',
    'Average',
    'Special',
    'Adorable',
    'Confused',
    'Impressed',
    'Devastating',
    'Pathetic',
    'Double');
$nouns = array(
    'Noob',
    'Potato',
    'Agent',
    'Dragon',
    'Sage',
    'Soldier',
    'Player',
    'Wolf',
    'Bear');

function generateName() {
    global $adjs, $nouns;
    $randNum = sprintf('%05d',rand(0,99999));
    $name = $adjs[array_rand($adjs)].$nouns[array_rand($nouns)].$randNum;
    return $name;
}

if($mode==1) {      //This one will make an array of generated name. (between quotes with a ,)
    for ($i = 0; $i <= $amountOfNames; $i++) {
        $currentUser = generateName();
        //echo $currentUser . "\n";     //writes the name in the CLI, but that's optional
        file_put_contents($fileName, "'$currentUser', ", FILE_APPEND);
    }
}

if($mode==2) {      //This will write one generated name per line
    for ($i = 0; $i <= $amountOfNames; $i++) {
        $currentUser = generateName();
        //echo $currentUser . "\n";     //writes the name in the CLI, but that's optional
        file_put_contents($fileName, $currentUser . "\n", FILE_APPEND);
    }
}

echo "Generated $amountOfNames names in '$fileName' in ". round((microtime(true) - $startTime), 3) ." seconds.";