php|architect's Guide to Web Scraping with PHP - Wind Business ...

PCRE Extension ” 153
• T ouse a literal ˆ character in a character range, either escape it in the same
manner in which other meta-characters are escaped or do not use it as the
first or only character in the range.
i
ctype Extension
Some simple patterns have equivalent functions available in the ctype library. These
generally perform better and should be used ov e r PCRE when appropriate. See
http://php.net/ctype for more information on the ctype extension and the functions
it offers.
M o d i fi e r s
The reason for having pattern delimiters to denote the start and end of a pattern
is that the pattern precedes modifiers that affect the matching behavior of metacharacters.
H e r e are a few modifiers that may prove useful in web scraping applications.
• i: Any letters in the pattern will match both uppercase and lowercase regardless
of the case of the letter used in the pattern.
• m: ˆ and $ will match the beginning and ends of lines within the string (delimited
by line feed characters) rather than the beginning and end of the entire
string.
• s (lowercase): The . meta-character will match line feeds, which it does not by
default.
• S (uppercase): Additional time will be spent to analyze the pattern in order
to speed up subsequent matches with that pattern. U s e f u lfor patterns used
multiple times.
• U: By default, the quantifiers * and + behave in a manner referred to as “ g r e e d y . ”
That is, they match as many characters as possible rather than as few as possible.
This modifier forces the latter behavior.