(PHP) Replace string of array elements using regex - php

Question

I have an array
Array
(
[0] => "http://example1.com"
[1] => "http://example2.com"
[2] => "http://example3.com"
...
)
And I want to replace the http with https of each elements using RegEx. I tried:
$Regex = "/http/";
$str_rpl = '${1}s';
...
foreach ($url_array as $key => $value) {
$value = preg_replace($Regex, $str_rpl, $value);
}
print_r($url_array);
But the result array is still the same. Any thought?

Answer 1

You actually print an array without changing it. Why do you need regex for this?
Edited with Casimir et Hippolyte's hint:
This is a solution using regex:
$url_array = array
(
0 => "http://example1.com",
1 => "http://example2.com",
2 => "http://example3.com",
);
$url_array = preg_replace("/^http:/i", "https:", $url_array);
print_r($url_array);
PHP Demo
Without regex:
$url_array = array
(
0 => "http://example1.com",
1 => "http://example2.com",
2 => "http://example3.com",
);
$url_array = str_replace("http://", "https://", $url_array);
print_r($url_array);
PHP Demo

Answer 2

First of all, you are not modifying the array values at all. In your example, you are operating on the copies of array values. To actually modify array elements:
use reference mark
foreach($foo as $key => &$value) {
$value = 'new value';
}
or use for instead of foreach loop
for($i = 0; $i < count($foo); $i++) {
$foo[$i] = 'new value';
}
Going back to your question, you can also solve your problem without using regex (whenever you can, it is always better to not use regex [less problems, simpler debugging, testing etc.])
$tmp = array_map(static function(string $value) {
return str_replace('http://', 'https://', $value);
}, $url_array);
print_r($tmp);
EDIT:
As Casimir pointed out, since str_replace can take array as third argument, you can just do:
$tmp = str_replace('http://', 'https://', $url_array);

Answer 3

This expression might also work:
^http\K(?=:)
which we can add more boundaries, and for instance validate the URLs, if necessary, such as:
^http\K(?=:\/\/[a-z0-9_-]+\.[a-z0-9_-]+)
DEMO
Test
$re = '/^http\K(?=:\/\/[a-z0-9_-]+\.[a-z0-9_-]+)/si';
$str = ' http://example1.com ';
$subst = 's';
echo preg_replace($re, $subst, trim($str));
Output
https://example1.com
The expression is explained on the top right panel of regex101.com, if you wish to explore/simplify/modify it, and in this link, you can watch how it would match against some sample inputs, if you like.
RegEx Circuit
jex.im visualizes regular expressions: