PHP Regular Expressions Reference

The following table lists the popular regular expressions.

Expression	Will match . . .
foo	The string "foo"
^foo	"foo" at the start of a line
foo$	"foo" at the end of a line
^foo$	"foo" when it is alone on a line
[Ff]oo	"Foo" or "foo"
[abc]	a, b, or c
[^abc]	d, e, f, g, V, %, ~, 5, etc.-everything that is not a, b, or c (^ is "not" inside character classes)
[A-Z]	Any uppercase letter
[a-z]	Any lowercase letter
[A-Za-z]	Any letter
[A-Za-z0-9]	Any letter or number
[A-Z]+	One or more uppercase letters
[A-Z]*	Zero or more uppercase letters
[A-Z]?	Zero or one uppercase letters
[A-Z]{3}	Three uppercase letters
[A-Z]{3,}	A minimum of three uppercase letters
[A-Z]{1,3}	One, two, or three uppercase letters
[^0-9]	Any non-numeric character
[^0-9A-Za-z]	Any symbol (not a number or a letter)
(cat\|sat)	Matches either "cat" or "sat"
([A-Z]{3}\|[0-9]{4})	Matches three letters or four numbers
PHP*	PH, PHPP, PHPPPP, etc.
PHP+	PHP, PHPP, PHPPPP, etc.
PHP?	PHP, PH
.	Any character except \n (new line)
\b	A word boundary; e.g. te\b matches the "te" in "late" but not the "te" in "tell."
\B	A non-word boundary; "te\B" matches the "te" in "tell" but not the "te" in "late."
\n	Newline character
\s	Any whitespace (new line, space, tab, etc.)
\S	Any non-whitespace character