Thinking about what you can use a regular expression for.
Understanding the difference between literals and metacharacters.
Using the metacharacters . (dot) and
| (bar).
Using the quantifiers *, +,
?,
{x},
{x,}, and
{x,y}.
Anchoring a regular expression with ^ or
$.
Anchoring a regular expression with \b or
\B.
Using a character class.
Using a negated character class.
Using character class metacharacters such as \d,
\D, \w, \W,
\s, and \S.
Understanding greed (in a regular expression context, at least).
Making quantifiers greedy or nongreedy.
Matching with preg_match( ).
Capturing with preg_match( ).
Matching and capturing with preg_match_all( ).
Using backreferences in a regular expression.
Replacing with preg_replace( ).
Using backreferences when replacing.
Making an array from a string with preg_split( ).
Selecting array elements with preg_grep( ).
