Question

I was having troubles with a simple thing, and after a long time trying to find out the problem I realize that str_replace does not work with simple quotes. This is my code:

<?php
$replaceNL1=str_replace("\n", "NEWLINE", $_POST['txt']);
echo $replaceNL1;
$replaceNL2=str_replace('\n', 'NEWLINE', $_POST['txt']);
echo '<hr>' . $replaceNL2;
?>

Only $replaceNL2 makes the replacement. On the first variable it acts like if there weren’t any str_replace(). This has never happened to me.

I am using UTF-8 charset.

Answer 1

Single and double quotes are a different thing in PHP.

PHP Strings:

Single quoted

The simplest way to specify a string is to enclose it in single quotes
(the character ‘).

To specify a literal single quote, escape it with a backslash (). To
specify a literal backslash, double it (\). All other instances of
backslash will be treated as a literal backslash: this means that the
other escape sequences you might be used to, such as \r or \n, will be
output literally as specified rather than having any special meaning.

So "\n" is newline character, whereas '\n' are two character (literaly \n) without special meaning.