PHP RegEx

A regular expression is a sequence of characters that forms a search pattern. When you search for data in a text, you can use this search pattern to describe what you are searching for.

A regular expression can be a single character, or a more complicated pattern.

Regular expressions can be used to perform all types of text search and text replace operations.

In PHP, regular expressions are strings composed of delimiters, a pattern and optional modifiers.

            $exp = "/analyzecode/i";
           

In the example above, / is the delimiter, analyzecode is the pattern that is being searched for, and i is a modifier that makes the search case-insensitive.

The delimiter can be any character that is not a letter, number, backslash or space. The most common delimiter is the forward slash (/), but when your pattern contains forward slashes it is convenient to choose other delimiters such as # or ~.

PHP provides a variety of functions that allow you to use regular expressions. The preg_match(), preg_match_all() and preg_replace() functions are some of the most commonly used ones:

Function	Description
preg_match()	Returns 1 if the pattern was found in the string and 0 if not
preg_match_all()	Returns the number of times the pattern was found in the string, which may also be 0
preg_replace()	Returns a new string where matched patterns have been replaced with another string

For example

<?php
// Sample text
$text = "The quick brown fox jumps over the lazy dog. 
        The quick brown dog jumps over the lazy cat.";

// Using preg_match() to find the first occurrence of "fox" or "dog"
$pattern = "/fox|dog/";
if (preg_match($pattern, $text, $matches)) {
    echo "First Match: " . $matches[0] . "\n";
} else {
    echo "No match found.\n";
}

// Using preg_match_all() to find all occurrences of "fox" or "dog"
if (preg_match_all($pattern, $text, $allMatches)) {
    echo "All Matches: " . implode(", ", $allMatches[0]) . "\n";
} else {
    echo "No matches found.\n";
}

// Using preg_replace() to replace "fox" or "dog" with "cat"
$replacementText = preg_replace($pattern, "cat", $text);
echo "Modified Text: " . $replacementText . "\n";
?>

Now that you have done functions in Php, let's learn functions in php

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