Regular expression to escape line breaks in a string

Question

I have a string in PHP that contains Python code, like below:

$source_code = "\nprint('Hello\nWorld')\n";

I need to escape line breaks between single or double quotes. I want to get something like the following:

$source_code = "\nprint('Hola\\nWorld')\n";

In other words, simply precede with an \ any occurrence of \n that is contained within single or double quotes. I have this in PHP for now in case single quotes are found:

<?php
    $source_code = "\nprint('Hello\nWorld')\n";
    $source_code = preg_replace("/'(.*)(\\n)(.*)'/", "\\n", $source_code);
    echo $source_code;
?>

But I am getting: \nprint(\n)\n . However, the expected string should be: \nprint('Hello\\nWorld')\n .

Thanks in advance!

Answer 1

you can use twice replacement, the first is remove the both ends "\n", and then replace the center \n

Answer 2

Works for single strings only. Feel free to extend if neccessary.

$source_code = "x=input()\nprint('Hello\nWorld')\n"; // thx for the test @Hugo :)

$match = preg_match('/(["\'])(.*)\1/s', $source_code, $matches);

if ($match) {
    $text = $matches[2];
    $text = str_replace("\n", '\\\\n', $text);
    $source_code = preg_replace('/(.*)((["\']).*\3)(.*)/s', '$1$3' . addslashes($text) . '$3$4', $source_code);
}

var_dump($source_code);

Wokring example .