PHP Regular expressions

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Regular expressions (regex) are a powerful tool for pattern matching in strings. PHP provides several functions for working with regular expressions, including preg_match(), preg_match_all(), preg_replace(), and preg_split().

For example, the preg_match() function can be used to check if a string matches a certain pattern. The following code will check if a string contains a valid email address:

if (preg_match("/^[a-zA-Z0-9._%+-][email protected][a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/", $email)) {
    echo "valid email address";
} else {
    echo "invalid email address";
}

The preg_match_all() function can be used to find all matches of a pattern in a string. The following code will find all occurrences of a word in a string:

preg_match_all("/\bword\b/", $string, $matches);
print_r($matches);

The preg_replace() function can be used to replace all occurrences of a pattern in a string with a replacement string. The following code will replace all occurrences of “cat” with “dog” in a string:

$new_string = preg_replace("/cat/", "dog", $string);

The preg_split() function can be used to split a string into an array based on a regular expression pattern. The following code will split a string into an array of words:

$words = preg_split("/\s+/", $string);
print_r($words);

It’s important to note that regular expressions can be complex and hard to read, so it’s a good idea to test your regular expressions before using them in production and use comments to explain the purpose and behavior of your regex.

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