Do I need to escape backslashes in PHP?

Question

Do I need to escape backslash in PHP?

echo 'Application\Models\User'; # Prints "Application\Models\User"
echo 'Application\\Models\\User'; # Same output
echo 'Application\Model\'User'; # Gives "Application\Model'User"

So it's an escape character. Shouldn't I need to escape it (\) if I want to refer to Application\Models\User?

Answer 1

In single quoted strings only the escape sequences \\ and \' are recognized; any other occurrence of \ is interpreted as a plain character.

So since \M and \U are no valid escape sequences, they are interpreted as they are.

Answer 2

In single quoted strings, it's optional to escape the backslash, the only exception is when it's before a single quote or a backslash (because \' and \\ are escape sequences).

This is common when writing regular expressions, because they tend to contain backslashes. It's easier to read preg_replace('/\w\b/', ' ', $str) than /\\w\\b/.

See the manual.

Answer 3

Since your last example contains a quote ('), you need to escape such strings with the addslashes function or simply adding a slash yourself before it like this:

'Application\Model\\'User'