Question

I have problem understanding this one:

<?php
$string = 'April 15, 2003';
$pattern = '/(\w+) (\d+), (\d+)/i';
$replacement = '${1}1,$3';
echo preg_replace($pattern, $replacement, $string);
?>

Output is April1,2003. I don’t understand this expression: $replacement = '${1}1,$3';
Would appreciate if somebody clarifies it for me.

Answer 1

Programmer had to use this, because

$replacement = '$11,$3'; 

would act weird and wrong. Also, they couldn’t use

$replacement = '$1'.'1,$3'; 

too,because it would cause it to be parsed as the first example.

That’s why there are these brackets, they work as a delimiter between the variable and number 1.

It’s the same as

$username = "Martin"
$text = "Hello ${username}and welcome";

above example will output “Hello Martinand welcome”

but this one

$username = "Martin";
$text = "Hello $usernameand welcome";

is mistchmashing the variable name with plain text, which is in your replacement, number 1