{"id":98,"date":"2014-01-05T03:29:19","date_gmt":"2014-01-05T03:29:19","guid":{"rendered":"http:\/\/www.webmastersun.com\/?p=98"},"modified":"2014-02-03T02:19:04","modified_gmt":"2014-02-03T02:19:04","slug":"regular-expression-php-tutorial","status":"publish","type":"post","link":"https:\/\/www.webmastersun.com\/blog\/regular-expression-php-tutorial\/","title":{"rendered":"Regular Expression PHP Tutorial"},"content":{"rendered":"

It takes the form:<\/p>\n

preg_match(‘\/regularexpression\/’, $textstring)<\/p>\n

Note the forward slash at the start and end of the regular expression. This is a way of indicating there is a regular expression between the forward slashes. Other PHP commands used with regexs are preg_split, preg_replace and preg_match_all. You can find out more of these from the official PHP website.<\/p>\n

Searching for an exact text phrase<\/strong><\/p>\n

If you want to check if an exact text string is within another text string, there are no special regex characters required – you just use the exact text phrase for the regular expression. For example:<\/p>\n

if (preg_match(‘\/tutorial\/’, ‘tips and tutorials are here for webmasters’))<\/p>\n

    echo “word ‘tutorial’ found!”;<\/p>\n

Note – it’s case sensitive. It’s actually more efficient to use the PHP function substrin these cases but I’m just kicking things off with an easy example.<\/p>\n

Start and end of text<\/strong><\/p>\n

If you’re searching for text at the start or end of a text file, use the symbols ^ and $.<\/p>\n

“^The”: matches any string that starts with “The”;<\/p>\n

“of despair$”: matches a string that ends in the substring “of despair”;<\/p>\n

Multiple characters<\/strong><\/p>\n

The symbols ‘*’, ‘+’, and ‘?’ denote the number of times a character or a sequence of characters may occur. What they mean respectively is: “zero or more”, “one or more”, and “zero or one”. For example:<\/p>\n

“tu*”: matches a string that has the letter t followed by zero or more u’s (“t”, “tu”, “tuuuuu”, “tutorial”, etc).<\/p>\n

“tu+”: similar but at least one u (“tu”, “tuuu”, “tut”, etc).<\/p>\n

“tu?”: there may or may not be a u.<\/p>\n

“t?b+$”: a possible t followed by one or more u’s ending the string.<\/p>\n

Or if you want to be more specific on the number of multiple characters, you can specify a range within braces {}.<\/p>\n

“o{3}h”: matches a string that has exactly three o’s followed by h (“oooh”).<\/p>\n

“o{3,}h”: there are at least three o’s (“oooh”, “ooooh”, “ooooooooooh”, etc).<\/p>\n

“o{3,5}h”: from three to five o’s (“oooh”, “ooooh”, or “oooooh”).<\/p>\n

You always specify the first number of a range but you can’t specify just the last number (eg – {3,5} or {3,} but not {,5}).<\/p>\n

If you want to quantify a sequence of characters rather than just a single character, put them inside parentheses:<\/p>\n

“t(ut)*”: matches a string that has an t followed by zero or more copies of the sequence “ut” (eg – “t”, “tut”, “tutututut”, etc).<\/p>\n

“t(ut){1,3}”: between one to three copies of “ut” (“tut”, “tutut”, “tututut”).<\/p>\n

OR operator<\/strong><\/p>\n

The ‘|’ symbol works as an OR operator: “tips|tutorials”: matches a string that has either “tips” or “tutorials” in it.<\/p>\n

“(b|cd)ef”: a string that has either “bef” or “cdef”.<\/p>\n

“(a|b)*c”: a string that has a sequence of alternating a’s and b’s ending in a c.<\/p>\n

Wild character<\/strong><\/p>\n

A period (‘.’) is a wild character – it can stand for any single character:<\/p>\n

“t.*p”: matches a string that has a t followed by any number of characters followed by a p (“tip”, “tp”, “tdfsadfsadsfp”, etc).<\/p>\n

“^.{5}$”: a string with exactly 5 characters (“bingo”, “blind”, “rainy”, “asdfe”, etc).<\/p>\n

Bracket expressions<\/strong><\/p>\n

Bracket expressions lets you match a whole range of characters to a single position of a string:<\/p>\n

“[tu]”: matches a string that has either a ‘t’ or a ‘u’ (that’s the same as “t|u”);<\/p>\n

“[a-d]”: a string that has lowercase letters ‘a’ through ‘d’ (that’s equal to “a|b|c|d” and even “[abcd]”);<\/p>\n

“^[a-zA-Z]”: a string that starts with a letter;<\/p>\n

“[0-9]%”: a string that has a single digit before a percent sign;<\/p>\n

“,[a-zA-Z0-9]$”: a string that ends in a comma followed by an alphanumeric character.<\/p>\n

Note that inside brackets, all the regex special characters are just ordinary characters – they don’t do any of their usual regular expression functions.<\/p>\n

Excluding characters<\/strong><\/p>\n

You can also exclude characters by using a ‘^’ as the first symbol in a bracket expression:<\/p>\n

“%[^a-zA-Z]%” matches a string with a character that is not a letter between two percent signs).<\/p>\n

Note – the difference between this application and using ^ at the start of a regular expression which specifies the first character of a string.<\/p>\n

Escaping regular expression characters<\/strong><\/p>\n

What do you do if you want to check for one of the regular expression special characters “^.[$()|*+?{\\” in your text string? You have to escape these characters with a backslash (‘\\’).<\/p>\n

Retrieving text using preg_match<\/strong><\/p>\n

If you want to extract a phrase out of a text string, you use the PHP function preg_match in the following format:<\/p>\n

preg_match(‘\/regular expression\/’, $textstring, $matchesarray)<\/p>\n

It returns a value of 1 if there is a match to your regular expression, a value of 0 if no match. For example,<\/p>\n

echo preg_match (‘\/test\/’, “a test of preg_match”);<\/p>\n

outputs 1 whereas<\/p>\n

echo preg_match (‘\/tutorial\/’, “a test of preg_match”);<\/p>\n

outputs 0.<\/p>\n

Preg_match is really useful for extracting phrases out of a text string. To do this, you specify an array as the third argument (eg – $matchesarray is what I use in the example). You also need to use parenthesizes in your regular expression to specify the sections you want to retrieve. If there’s a successful match, $matchesarray is filled with the results of the search. $matchesarray[0] contain the entire text string. $matchesarray[1] contains the text that matched the first captured parenthesized subpattern, and so on.<\/p>\n

For example, the following regex divides a url into two sections. The first section is “http:\/\/” (note the escaping back slash), the second section is whatever comes after:<\/p>\n

preg_match (‘\/(http:\/\/)(.*)\/’, “https:\/\/www.webmastersun.com\/”, $matchesarray)<\/p>\n

This fills $matchesarray with the following values:<\/p>\n

$matchesarray[0] = “https:\/\/www.webmastersun.com\/”<\/p>\n

$matchesarray[1] = “http:\/\/”<\/p>\n

$matchesarray[2] = “www.webmastersun.com\/”<\/p>\n","protected":false},"excerpt":{"rendered":"

It takes the form: preg_match(‘\/regularexpression\/’, $textstring) Note the forward slash at the start and end of the regular expression. This is a way of indicating there is a regular expression between the forward slashes. Other PHP commands used with regexs are preg_split, preg_replace and preg_match_all. You can find out more of these from the official […]<\/p>\n","protected":false},"author":1,"featured_media":99,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"class_list":["post-98","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-articles"],"yoast_head":"\nRegular Expression PHP Tutorial - Webmaster Sun Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.webmastersun.com\/blog\/regular-expression-php-tutorial\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Regular Expression PHP Tutorial - Webmaster Sun Blog\" \/>\n<meta property=\"og:description\" content=\"It takes the form: preg_match(‘\/regularexpression\/’, $textstring) Note the forward slash at the start and end of the regular expression. 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