RegEx practice

regex_practice.php

<?php

$string = "This website is stupid.  Your speaking style is idiotic.  Your knowledge is crap.This is so stupid. You are an idiot. You are an IDIOT!";
echo preg_replace('/stupid|idiot(?:ic)?|crap/i', 'amazing', $string) . PHP_EOL . PHP_EOL;

$website1 = 'www.laracasts.com';
$website2 = 'alexrusin.com';
echo preg_replace('/www\.([^\.]+)/i', '$1', $website1) . PHP_EOL;
echo preg_replace('/www\.([^\.]+)/i', '$1', $website2) . PHP_EOL . PHP_EOL;

$phrase = 'Thanks for help, @JohnDoe.
@JohnDoe, thanks for the help!
@JonDoe rocks!';
echo preg_replace('/@(\w+)/i', '<a href="https://google.com/$1">@$1</a>', $phrase) . PHP_EOL . PHP_EOL;

// (?=string)
// (?!string)
$lookAhead = '<a href="http://google.com">Google</a>
google.com is the best search engine.';
echo preg_replace('/google(?=<)/i', 'Change', $lookAhead) . PHP_EOL;
echo preg_replace('/google(?!<)/i', 'Change', $lookAhead) . PHP_EOL . PHP_EOL;
// (?<=string)
// (?<!string)
$lookBehind = '$name = "Quaid"; My name is Quaid';
echo preg_replace('/(?<=\$)name/i', 'VARIABLE', $lookBehind) . PHP_EOL;
echo preg_replace('/(?<!\$)name/i', 'VARIABLE', $lookBehind) . PHP_EOL . PHP_EOL;

$message = "Listen, Centari, I'm not any of those guys.  I'm a kid from a trailer park. Okay, centauri?";

if (stristr($message, 'Centauri')) {
    var_dump('We found it');
}

if (preg_match('/Centau?ri/i', $message)) {
    var_dump('We found it');
}

preg_match('/Centau?ri/i', $message, $matches);
var_dump($matches);
preg_match_all('/Centau?ri/i', $message, $matches);
var_dump($matches);

var_dump(preg_replace('/Centau?ri/i', 'John', $message));

$message = "  foo    , bar, baz  ";
$message = trim($message);
$array  = preg_split('/\s*,\s*/', $message);

var_dump($array);

$comments = [
    "Always trust Centauri.",
    "You almost got me killed.",
    "You are the man, dog.",
    "Listen, Centari. I'm not any of those guys, I'm a kid from trailer park."
];

$filtered = array_filter($comments, function($comment){
    return preg_match('/Centau?ri/i', $comment);
});

var_dump($filtered);

$filtered = preg_grep('/Centau?ri/i', $comments);
var_dump($filtered);