{"id":561,"date":"2010-01-22T12:17:24","date_gmt":"2010-01-22T12:17:24","guid":{"rendered":"http:\/\/www.codingfriends.com\/?p=561"},"modified":"2010-01-22T12:19:37","modified_gmt":"2010-01-22T12:19:37","slug":"regular-expression-php","status":"publish","type":"post","link":"https:\/\/www.codingfriends.com\/index.php\/2010\/01\/22\/regular-expression-php\/","title":{"rendered":"Regular expression – PHP"},"content":{"rendered":"

Regular expression<\/a> is when you have a match condition and a string to search through. Here is a cheat sheet<\/a> to download to view regular expressions syntax.<\/p>\n

The regular matching method in php that I use is preg_match_all<\/p>\n

\r\nint preg_match_all ( string pattern, string subject, array &matches [, int flags [, int offset]] )\r\n<\/pre>\n
which basically means that it will return a integer value of how many matches it has found within the subject text.  The flags and offset are optional values.<\/p>\n
Here is a example to pull out HTML A links within a text, A links start with <a and have some optional parameters e.g. href, title >text to display on the screen<\/a> (the closing tag.  So in xml speak as such<\/p>\n
\r\nvalue<\/a>\r\n<\/pre>\n
So the basics of searching for HTML A links within a string is to look for “” which then has the value and then the closing tag <\/a>.  So to put that in regular expression talk, to break it down we first search for the start <a<\/strong> followed by x amount of characters \\s.*<\/strong> with a ending tag of <\\\/a><\/strong> the “\\” is there because the \/ is a condition statement for regular expression.  And with this together it would look like<\/p>\n
\r\n\r\n<\/pre>\n
But because <\\\/a> happens twice in the string and either one can be the end point of the search since we are searching string values “\\s.*” 0-x amount of them.  \\s means white space character “.” means any character that is not \\n and “*” means 0 – more times of the previous check.  So there is potential for a problem here we are not telling the regular expression to stop at the first < character and to this we use the [] to match some characters, the ^ in this context means any character not in this list about to come and \"<\" is the stopping character.  So the full regular expression will be.\n\n\n\n
\r\n\r\n<\/pre>\n
Here is the php code that will display all of the HTML A links from a string.<\/p>\n
\r\ncodingfriends.com<\/a> hi there.. \" . \r\n\t    \" mountains are nice. norfolkhospice.org.uk<\/a>\" . \r\n\t    \" support the tapping house in Norfolk\";\r\n\r\n\/\/ the preg_match_all uses regular expression to match and pull out strings, $matches is the matches found.\r\n\r\n$matched = preg_match_all(\"\/\/\",$matchAStr,$matches);\r\necho \"There was $matched matche(s)\\n\";\r\n\r\necho \"
    \\n\";\r\nforeach($matches[0] as $url)\r\n{\r\n  echo \"
  1. \".$url.\"<\/li>\\n\";\r\n}\r\necho \"<\/ol>\\n\";\r\n?>\r\n<\/pre>\n
    \r\nThere was 2 matche(s)\r\n
      \r\n
    1. codingfriends.com<\/a><\/li>\r\n
    2. norfolkhospice.org.uk<\/a><\/li>\r\n<\/ol>\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
      Regular expression is when you have a match condition and a string to search through. Here is a cheat sheet to download to view regular expressions syntax. The regular matching method in php that I use is preg_match_all int preg_match_all ( string pattern, string subject, array &matches [, int flags [, int offset]] ) which … Continue reading Regular expression – PHP<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[64],"class_list":["post-561","post","type-post","status-publish","format-standard","hentry","category-php","tag-regular-expression"],"_links":{"self":[{"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/posts\/561","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/comments?post=561"}],"version-history":[{"count":5,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/posts\/561\/revisions"}],"predecessor-version":[{"id":565,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/posts\/561\/revisions\/565"}],"wp:attachment":[{"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/media?parent=561"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/categories?post=561"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/tags?post=561"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}