How Can PHP\'s `preg_match_all()` Function Be Used to Find Multiple Occurrences of a Pattern in a String?

Finding Multiple Occurrences with PHP preg_match

php preg_match_all() is an invaluable function for finding multiple occurrences of a specific string or pattern within a given text. This capability is essential in various text processing applications.

Syntax and Usage

To leverage preg_match_all() effectively, it's crucial to understand its syntax:

int preg_match_all(string $pattern, string $subject, array &$matches [, int $flags = PREG_PATTERN_ORDER])

In essence, $pattern represents the search pattern or regular expression, $subject is the target string or text being searched, $matches is an array where the found occurrences will be stored, and $flags allows customization of the matching process.

Multiple Occurrence Detection

To illustrate its usage in detecting multiple occurrences, consider the following PHP code:

$string = "/brown fox jumped [0-9]/";
$paragraph = "The brown fox jumped 1 time over the fence. The green fox did not. Then the brown fox jumped 2 times over the fence";

if (preg_match_all($string, $paragraph, $matches)) {
    echo count($matches[0]) . " matches found";
} else {
    echo "match NOT found";
}

In this snippet, we search for multiple occurrences of the string /brown fox jumped [0-9]/ within the $paragraph variable. The regular expression captures any occurrence of the phrase "brown fox jumped" followed by a space, a digit, and a closed square bracket.

If this pattern is found at least once within the paragraph, the if block will execute, and the counter for the number of found matches will be printed. Conversely, if no matches are found, the else block will indicate no occurrence.

In this example, the output would be:

2 matches found

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