(PHP) Replace string of array elements using regex

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:

1. use reference mark

foreach($foo as $key => &$value) {
   $value = 'new value';
}

2. 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: