Optimizing Regex Usage in PHP

Regular expressions are very heavy and relatively slow-performing things. When there is an alternative solution, it is advisable to use it.

Let's look at an example. Suppose we need to check if a certain string starts with an exclamation mark. A certain programmer solved this problem via a regex:

<?php
	if (preg_match('#^!#', $str)) {
		echo 'yes';
	} else {
		echo 'no';
	}
?>

However, such a task has a much faster solution:

<?php
	if ($str[0] == '!') {
		echo 'yes';
	} else {
		echo 'no';
	}
?>

Regexes are very heavy and relatively slow-performing things. Always, where there is an alternative solution, it is advisable to use it.

In the following code, a certain programmer checks if the string contains the substring '333'. Optimize this programmer's solution.

Here is the code:

<?php
	$str = '1233345';
	
	if (preg_match('#333#', $str)) {
		echo 'exists';
	} else {
		echo 'does not exist';
	}
?>

In the following code, a certain programmer checks if the string ends with .html. Optimize this programmer's solution.

Here is the code:

<?php
	$str = 'index.html';
	
	if (preg_match('#\.html$#', $str)) {
		echo 'yes';
	} else {
		echo 'no';
	}
?>

Write code that will check if the string ends with .png or with .jpg.