Regex to remove single characters from string

Question

Consider the following strings

breaking out a of a simple prison
this is b moving up
following me is x times better

All strings are lowerca

Answer 1

You could try something like this:

preg_replace('/\b\S\s\b/', "", $subject);

This is what it means:

\b    # Assert position at a word boundary
\S    # Match a single character that is a “non-whitespace character”
\s    # Match a single character that is a “whitespace character” (spaces, tabs, and line breaks)
\b    # Assert position at a word boundary

Update

As raised by Radu, because I've used the \S this will match more than just a-zA-Z. It will also match 0-9_. Normally, it would match a lot more than that, but because it's preceded by \b, it can only match word characters.

As mentioned in the comments by Tim Pietzcker, be aware that this won't work if your subject string needs to remove single characters that are followed by non word characters like test a (hello). It will also fall over if there are extra spaces after the single character like this

test a  hello 

but you could fix that by changing the expression to \b\S\s*\b