How can PHP variables be properly used within regular expressions to avoid errors?

When using PHP variables within regular expressions, it is important to properly escape the variables to avoid errors caused by special characters. This can be achieved by using the `preg_quote()` function to escape the variable before inserting it into the regular expression pattern. This ensures that the variable's value is treated as a literal string rather than a pattern to match. 

// Example of using preg_quote() to escape a PHP variable within a regular expression
$keyword = "example";
$text = "This is an example text.";
$escaped_keyword = preg_quote($keyword, '/');
if (preg_match('/\b' . $escaped_keyword . '\b/', $text)) {
    echo "Keyword found!";
} else {
    echo "Keyword not found.";
}

Keywords

PHP variables regular expressions errors validation

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