Alternation
Anchors
Assertions
Back references
characterswithvaluesgreaterthan128donotmatchanyofthePOSIXcharacterclasses.AsofPHP5.3.0andlibpcre8.10somecharacterclassesarechangedtouseUnicodecharacterproperties,inwhichcasethementionedrestrictiondoesnotapply.Refertothe»PCRE
Comments
Conditional subpatterns
Delimiters
Dot
Escape sequences
Internaloptionsetting ThesettingsofPCRE_CASELESS,PCRE_MULTILINE,PCRE_DOTALL,PCRE_UNGREEDY,PCRE_EXTRA,
Introduction
Meta-characters
Once-only subpatterns
)Ifthismodifierisset,lettersinthepatternmatchbothupperandlowercaseletters.m(PCRE_MULTILINE)Bydefault,
Performance
eachalternativebranchofalookbehindassertioncanmatchadifferentlengthofstring.Perl5.005requiresthemalltohavethesamelength.2.If[PCRE
Recursive patterns
Repetition
Subpatterns