CODEWITHSUNDEEP
phparraysstr-replace
Halil Yıldırım
Halil Yıldırım

Reputation: 45

php array and str_replace working together

    <?php
$search = array("cencor","cencors");
$change = array("prohibited","***");
if(isset($_POST['submit']) AND !empty($_POST['text'])){
$text = $_POST['text'];
$text = str_replace($search,$change,$text);
}
?>
<form action="index.php" method="post">
    <textarea name="text"><?php echo $text;?></textarea>
    <input type="submit" name="submit">
</form>

Hello I am using this code. I have a problem with this code that when I submit

Don't use cencor and cencors

It returns

Don't use prohibited and prohibiteds

I want to get result like

Don't use prohibited and ***

How can I do that? Thank you!

Upvotes: 2

Views: 64

Answers (1)

Scoots
Scoots

Reputation: 3102

There's something to be wary of on this front, and that is that some words are substrings of others.

I remember reading an article on the subject a few years ago, and it was titled something like "The Clbuttic Mistake". The article went into detail how a poorly implemented profanity filter can create as many problems as it solves. This particular article showed the pitfalls of exactly the same method as you are using in your question.

The replacement they focused on was naturally $content = str_replace('ass', 'butt', $content);. This yielded some amusing transformations, such as "assassinate" becoming "buttbuttinate".

This is exactly the same issue you are seeing, because "cencor" is a substring of "cencors". Even though you intend to replace both, you're still seeing the same problem.

The solution is to be much more targeted in the way you do your replacements, by making sure that you only match on a full word. You can do this with a regex based approach:

<?php

$replacements = array(
    "cencor" => "prohibited",
    "cencors" => "***"
);

$text = "Don't use cencor, and cencors";

foreach($replacements as $search => $change) {
    $text = preg_replace("~(^|[\s\W])" . preg_quote($search, '~') . "([\s\W]|$)~ism", "\\1{$change}\\2", $text);
}

echo $text;

Upvotes: 2

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