Regular Expression Basics Literals bus Matches a ‘ b ’, followed by a ‘ u ’, followed by an ‘ s ’

Regular Expression Basics Anchors ^ Matches at the beginning of a line $ Matches at the end of a line

Regular Expression Basics Character Classes [abc] Matches one of ‘ a ’, ‘ b ’ or ‘ c ’ [a-c] Same as above (character range) [^abc] Matches one character that is not listed . Matches any single character

Regular Expression Basics Alternation a|b Matches one of ‘ a ’ or ‘ b ’ dog|cat Matches one of “dog” or “cat”

Regular Expression Basics Quantifiers (repetition) {x,y} Matches minimum of x and a maximum of y occurrences; either can be omitted * Matches zero or more occurrences (any amount). Same as {0,} + Matches one or more occurrences. Same as {1,} ? Matches zero or one occurrences. Same as {0,1}

Regular Expression Basics Grouping (…) Groups the contents of the parentheses. Affects alternation and quantifiers. Allows parts of the match to be captured for|backward “ for” or “backward” (for|back)ward “ forward” or “backward”

Regular Expression Basics Delimiters pattern / modifiers / /i Makes match case-insensitive

Testing for a Substring if ( preg_match ( '/foo/' , $ var )) if ( strpos ( $ var , 'foo' ) !== false ) if ( preg_match ( '/foo/i' , $ var )) if ( stripos ( $ var , 'foo' ) !== false )

HTML Parsing

Using Regular Expressions

Using Regular Expressions Postcodes /[A-Z]{1,2}[0-9R][0-9A-Z]? [0-9][A-Z]{2}/ IP Addresses @^({1,2})/({1,2})/({4})$@

You don’t need to use /…/ to denote a pattern! /…/ to denote a pattern! preg_match ( '/<b><s> .+ < s> .+ < b>/' , $ html ) preg_match ( '@<b><s> .+ </s> .+ </b>@' , $ html )

Greediness $ html = <<< HTML <span> some text </span><span> some more text! </span> HTML ; preg_match ( &quot;@<span>(.+)</span>@&quot; , $ html , $ matches ); echo $ matches [ 0 ]; preg_match ( &quot;@<span>(.+?)</span>@&quot; , $ html , $ matches ); echo $ matches [ 0 ];

You can make your pattern readable! preg_match ( '`^(+)://(?:(.+?):(.+?)@)?(.+?)(+)$`' , $ s , $ matches ) preg_match ( '` ^ (+):// # Protocol (?: (.+?) # Username : # : (.+?) # Password @ # @ )? # Username/password are optional (.+?) # Hostname (+) # Top-level domain $ `x' , $ s , $ matches );

Extracting Captures preg_match ( '`^ (?P<protocol>+):// (?: (?P<user>.+?) : (?P<pass>.+?) @ )? (?P<host>.+?) (?P<tld>+) $`x' , $ s , $ matches ); Array( [0] => http://foo:bar@baz.example.com [protocol] => http [1] => http [user] => foo [2] => foo [pass] => bar [3] => bar [host] => baz.example [4] => baz.example [tld] => com [5] => com) preg_match ( '`^ (?P<protocol>+):// (?: (?P<user>.+?) : (?P<pass>.+?) @ )? (?P<host>.+?) (?P<tld>+) $`x' , $ s , $ matches );

Variable Data if ( preg_match ( &quot;!> $ value </(?:div|span)>!&quot; , $ text )) $ value = preg_quote ( $ value , '!' );

Any Questions?