PHP Regular Expressions

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PHP Regular Expressions (or regex) are a powerful tool for matching and manipulating text. They allow you to search for patterns in strings and perform operations on them. Here are some basic examples of using regular expressions in PHP:

  1. Matching a string: You can use the preg_match() function to search for a pattern in a string. For example, to check if a string contains the word “hello”, you can do:
bashCo$string = "Hello, world!";
if (preg_match("/hello/i", $string)) {
    echo "String contains 'hello'";
} else {
    echo "String does not contain 'hello'";
}

In this example, the "/hello/i" pattern means to match the word “hello” case-insensitively. The i flag at the end of the pattern specifies case-insensitive matching.

  1. Replacing a string: You can use the preg_replace() function to replace parts of a string that match a pattern. For example, to replace all occurrences of the word “world” with “universe”, you can do:
$string = "Hello, world!";
$new_string = preg_replace("/world/i", "universe", $string);
echo $new_string; // Output: "Hello, universe!"

In this example, the "/world/i" pattern matches the word “world” case-insensitively, and the replacement string is “universe”.

  1. Extracting parts of a string: You can use capture groups to extract parts of a string that match a pattern. For example, to extract the first name from a string in the format “Last, First”, you can do:
$string = "Doe, John";
if (preg_match("/(\w+),\s*(\w+)/", $string, $matches)) {
    $last_name = $matches[1];
    $first_name = $matches[2];
    echo "First name: $first_name, last name: $last_name";
} else {
    echo "String does not match pattern";
}

In this example, the pattern "/(\w+),\s*(\w+)/" matches a word (one or more alphanumeric characters) followed by a comma, optional whitespace, and another word. The parentheses around \w+ create capture groups, which can be accessed using the $matches array.

These are just a few examples of the many things you can do with regular expressions in PHP. You can find more information in the PHP documentation: https://www.php.net/manual/en/book.pcre.php

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