Replace with dynamic variable in preg_replace - php

Question

I'm getting stuck at this problem, which is
I have an array like this:
$array = [
'name' => 'John',
'email' => john#gmail.com
];
And a string sample like this:
$string = 'Hi [[name]], your email is [[email]]';
The problem is obvious, replace name with John and email with john#gmail.com.
What i attempted:
//check if $string has [[ ]] pattern
$stringHasBrackets = preg_match_all('/\[\[(.*?)\]\]/i', $string, $matchOutput);
if ($stringHasBrackets) {
foreach ($matchOutput[1] as $matchOutputKey => $stringToBeReplaced) {
if (array_key_exists($stringToBeReplaced, $array)) {
$newString = preg_replace("/\[\[(.+?)\]\]/i",
$array[$stringToBeReplaced],
$string);
}
}
}
Which led me to a new string like this:
Hi john#gmail.com, your email is john#gmail.com
Makes sense because that's what the pattern is for, but not what I wanted.
How can I solve this? I thought of using a variable in the pattern but don't know how to do it. I've read about preg_replace_callback but also don't really know how to implement it.
Thanks!

Answer 1

You may use preg_replace_callback like this:
$array = ['name' => 'John', 'email' => 'john#gmail.com'];
$string = 'Hi [[name]], your email is [[email]]';
echo preg_replace_callback('/\[\[(.*?)]]/', function ($m) use ($array) {
return isset($array[$m[1]]) ? $array[$m[1]] : $m[0];
}, $string);
See PHP demo.
Details
'/\[\[(.*?)]]/' matches [[...]] substrings putting what is inside the brackets into Group 1
$m holds the match object
use ($array) allows the callback to access $array variable
isset($array[$m[1]]) checks if there is a value corresponding to the found key in the $array variable. If it is found, the value is returned, else, the found match is pasted back.

Answer 2

preg_replace accepts arrays as regex and replacement so you can use this simpler approach:
$array = ['name' => 'John', 'email' => 'john#gmail.com'];
$string = 'Hi [[name]], your email is [[email]]';
// create array of regex using array keys
$rearr = array_map(function($k) { return '/\[\[' . $k . ']]/'; },
array_keys($array));
# pass 2 arrays to preg_replace
echo preg_replace($rearr, $array, $string) . '\n';
Output:
Hi John, your email is john#gmail.com
PHP Code Demo

Answer 3

You can try this,
$array = ['name' => 'John', 'email' => 'john#gmail.com'];
$string = 'Hi [[name]], your email is [[email]]';
$stringHasBrackets = preg_match_all('/\[\[(.*?)\]\]/i', $string, $matchOutput);
if ($stringHasBrackets) {
$newString = $string;
foreach ($matchOutput[1] as $matchOutputKey => $stringToBeReplaced) {
if (array_key_exists($stringToBeReplaced, $array)) {
$newString = preg_replace("/\[\[$stringToBeReplaced\]\]/i", $array[$stringToBeReplaced], $newString);
}
}
echo $newString;
}

Answer 4

I think here more simply would be to use str_replace function, like:
$array = [
'name' => 'John',
'email' => 'john#gmail.com'
];
$string = 'Hi [[name]], your email is [[email]]';
$string = str_replace(array_map(function ($v) {return "[[{$v}]]";},
array_keys($array)), $array, $string);
echo $string;
Updated for $array to be "untouchable"