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

How about:

preg_replace('/(^|\s)[a-z](\s|$)/', '$1', $string);

Note this also catches single characters that are at the beginning or end of the string, but not single characters that are adjacent to punctuation (they must be surrounded by whitespace).

If you also want to remove characters immediately before punctuation (e.g. 'the x.'), then this should work properly in most (English) cases:

preg_replace('/(^|\s)[a-z]\b/', '$1', $string);