{"id":1288,"date":"2018-01-19T19:22:39","date_gmt":"2018-01-19T19:22:39","guid":{"rendered":"http:\/\/goofy-trucks.flywheelsites.com\/advanced-string-processing-how-regular-are-your-expressions\/"},"modified":"2018-01-19T19:24:40","modified_gmt":"2018-01-19T19:24:40","slug":"advanced-string-processing-how-regular-are-your-expressions","status":"publish","type":"post","link":"https:\/\/phpbuilder.com\/advanced-string-processing-how-regular-are-your-expressions\/","title":{"rendered":"Advanced String Processing – How Regular Are Your Expressions"},"content":{"rendered":"
\n
\n
By PHP Builder Staff<\/div>\n
on May 19, 2009<\/div>\n<\/p><\/div>\n
\n
\nIntroduction\n<\/div>\n
Hello hello hello, and welcome
\nback. We’ve looked at strings, and numbers and all sorts of
\ntypes of data, but we’ve not yet seen how to do something
\nreally important, and that’s to look for and pull
\ninteresting parts out of the data we have, to do that where
\ngoing to use some magic from the Perl world called “Regular
\nExpressions” <\/div>\n
\nHuh, Regular What?\n<\/div>\n
Put simply, a regular expression
\nis a string in it’s own right, but one that has a special
\nmeaning. In some ways it’s like a little mini program that
\ntells the regexp engine what to look for and how to find it.\n<\/div>\n
Look at the first line of my
\nopening paragraph above. <\/div>\n
If you wanted to look for that
\n“Hello hello hello” and treat it as a spelling error to
\ncorrect how are you going to find it? <\/div>\n
\nWell you could use\n<\/div>\n

\n
\nif($text == \"Hello hello hello\")
\n<\/code>\n<\/p>\n

\nor you might use the text function “str_replace<\/code>“:\n<\/div>\n

\n
\nstr_replace(\"Hello hello hello\",\"Hello\");
\n<\/code>\n<\/p>\n

and they would work fine, but what
\nif we now made the phrase “Hello hello hullo”? hmmm, it
\nlooks like we now don’t have a match. This is where the
\npower of regular expressions comes to the rescue. <\/div>\n
\nHow do Regular Expressions Work Then?\n<\/div>\n
Ok, so your asking yourself, how
\ncan I match something that’s not match-able unless I change
\nwhat I’m looking for, which is not what I want to do. <\/div>\n
The key is not to change what your
\nsearching for but, to just search for the differences.\n<\/div>\n
It’s a set of searching rules,
\nthat allows for variations in the text to be searched.\n<\/div>\n
What exactly is the difference
\nbetween “Hello hello hello” and “Hello hello hullo” , well
\nin this case it’s only one letter, and that letter can be
\neither an ‘e’ or a ‘u’, if we had a way of just saying
\nsearch for this phrase, but at the 4th letter from the end,
\nyou need to be aware that that could change, then you’ve
\npretty much defined what a regular expression is. <\/div>\n
Now in our example here, we could
\nactually expand that very easily, to be aware of any letter
\nat that position and not just a ‘e’ or ‘u’, we do this by
\nusing the full stop operator ‘.<\/code>‘ , so to show
\nyou what I mean we could write our search pattern like this:\n<\/div>\n

\n
\n\"Hello hello h.llo\"
\n<\/code>\n<\/p>\n<\/p>\n

That will match any character at
\nthat position, but only one character, all the rest have to
\nmatch. <\/div>\n
There is however much more to the
\npower of reg-expressions than just single letters, we can
\nsearch for whole groups of numbers, letters and combinations
\nof words symbols. Also for certain counts and lengths.\n<\/div>\n
There’s far more than we can cover
\nin this article, developing a true mastery of reg-
\nexpressions takes years. We only have time to cover what you
\nneed to know to get you started in PHP. <\/div>\n
Once snippet of advice I will
\ngive, find a program that will allow you to see what your
\ndoing as you construct regular expressions. I use the
\nwonderful reg-ex coach available from http:\/\/weitz.de\/regex-
\ncoach\/<\/a> There is an older version for linux, but the
\nlatest versions are only maintained under Windows now, it
\ndoes however run perfectly fine under wine. <\/div>\n<\/div>\n

<\/p>\n

\n
1<\/div>\n
| <\/div>\n
2<\/a> <\/div>\n
| <\/div>\n
3<\/a> <\/div>\n
Next Page \u00bb<\/a><\/div>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"

This week Peter Shaw shows us the power of regular expressions, the building blocks of PHP, and what they can do for<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-1288","post","type-post","status-publish","format-standard","hentry","category-tutorials"],"_links":{"self":[{"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/posts\/1288","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/comments?post=1288"}],"version-history":[{"count":1,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/posts\/1288\/revisions"}],"predecessor-version":[{"id":3181,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/posts\/1288\/revisions\/3181"}],"wp:attachment":[{"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/media?parent=1288"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/categories?post=1288"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/tags?post=1288"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}