What is the recommended approach in PHP to replace all characters in a string that are not letters or numbers with a specific pattern?

To replace all characters in a string that are not letters or numbers with a specific pattern in PHP, you can use a regular expression with the `preg_replace` function. The regular expression pattern `[^a-zA-Z0-9]` matches any character that is not a letter or a number. You can then replace these characters with your desired pattern, such as an underscore or an empty string. 

$string = "Hello, World!123";
$pattern = '/[^a-zA-Z0-9]/';
$replacement = '_';

$new_string = preg_replace($pattern, $replacement, $string);

echo $new_string; // Output: Hello_World123

Keywords

PHP string manipulation regular expressions preg_replace character filtering

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