In PHP, what are the differences between using substr_count and preg_match for manipulating strings?

When manipulating strings in PHP, the main difference between using substr_count and preg_match is that substr_count is used to count the occurrences of a substring within a string, while preg_match is used to search for a pattern within a string using a regular expression. If you need to simply count the occurrences of a specific substring, substr_count is more efficient and straightforward. If you need to search for more complex patterns using regular expressions, then preg_match is the appropriate choice.

// Using substr_count to count occurrences of a substring
$string = "Hello, World! Hello, Universe!";
$substring = "Hello";
$count = substr_count($string, $substring);
echo $count; // Output: 2

// Using preg_match to search for a pattern using a regular expression
$string = "The quick brown fox jumps over the lazy dog";
$pattern = "/\b[a-zA-Z]{5}\b/"; // Search for words with exactly 5 characters
preg_match_all($pattern, $string, $matches);
print_r($matches[0]); // Output: Array ( [0] => quick [1] => brown )