Replace class in table using preg_replace

[dseegersmail]

Hey Everyone,

I have this string below, now I want to replace class from all tables (only the classes).
What is the best way to do this using a preg_replace?

<table border="0" cellpadding="0" cellspacing="0" id="sheet0" class="sheet0 gridlines tablepress tablepress--matrix">

[m_hutley]

… why?

Surely this is easier to do by editing the HTML, rather than trying to use a backend engine to replace it on every page load.

[dseegersmail]

It comes from a parser, is it is not replaced on every pageload

[m_hutley]

Again, it would be easier to change the source than to do it programmatically.

Anyway. What have you tried so far? You’ve said you want to do it with preg_replace, so… what’s your current pattern?

[dseegersmail]

I started with this <table class(.*?)>

[m_hutley]

Mkay. So let’s consider what you actually want.

• You want table tags.
• You only want to modify the class part of it.
• Table tags can have many attributes.
• The class attribute is not always in the same place.
• Class attributes will have the form of:
  • the word class
  • optionally a space.
  • an equals sign
  • optionally another space.
  • a string, encapsulated either with a pair of single quotes, or a pair of double quotes. (If you want to specify that your code only finds double-quoted strings, so be it.)

So; give me a pattern that says the following.

Inside a table tag, find three subpatterns: Everything before the class attribute, the class attribute, and then everything after the class attribute.

[dseegersmail]

<table.class="(.*?)".>

[m_hutley]

(You had it nearly right the first time. You need to capture all 3 subpatterns, and they need to capture as many characters as necessary, non-greedily.)

So; you’ve now got the building blocks to build your replacement text with.

Backreferences are the key here. Manual source, if needed.

Your replacement string is the string <table, the first subpattern, the string class=", your replacement class(es), the string ", the third subpattern, and then the string >

[dseegersmail]

First of all, thank you for the reply.

When I do this <table.class="(.*?)".>
I only get the first line

RegExr: Learn, Build, & Test RegEx

[m_hutley]

apply the g modifier.
(By default, PCRE will stop after the first match. You have to tell it to search globally.)

[dseegersmail]

Okay lets say I want to do this in PHP

And I have this replacement

$rawDataFromSheetData = preg_replace("/<table.class=\"(.*?)\".>/gmU", "babs", $rawDataFromSheetData);

I get this message Warning: preg_replace(): Unknown modifier 'g' in.

Beside that it will replace the complete string? (if it is working)

[dseegersmail]

@dseegersmail

When I do this <table.class="(.*?)".>
I only get the first line

Needed to be
(<table.*class=")(.*?)(".*>) Since it was not only one space

[m_hutley]

preg_replace automatically globalizes its search.

So you’ve got the blocks; your replacement string at that point would be "\1babs\3" (“the first subpattern, then your replacement, then the third subpattern”)

[rpkamp]

@dseegersmail

(<table.*class=")(.*?)(".*>)

That first .* should be lazy instead of greedy like it is now. Otherwise it might just match the class of a differt tag that follows the table.
Also, the last construct can be a bit more efficient like this ([^"]*)" - which means, 0 or more times anything but a double quote, followed by a double quote.

So in total it would become (<table.*?class=")([^"]*)" and then the replacement would become \1babs".

[dseegersmail]

Hey @rpkamp,

I am always really happy if you are responding. Since you give a lot of good advice (Thank you for it ).

What if you want to change only the classes in a PHP preg_replace. (Since that the thing is I wanted to do in the First place). (<table.class=")(.?)(“.*>) in the middle, I group the classes and replace them. with another class. But (<table.*?class=")([^"]*) has only two selectors (everything between <table *** class=”). And the second I not really get.

It is a negative set, so it will get everything except the " ?. How do you all the classes? Or will it until it finds the "?

[m_hutley]

Because your class is greedy (*), it will consume all characters until it sees a double-quote, but it will not consume said double quote; that said, the way you have written it, [^"]*\w will never match anything, because you’re saying "Consume everything until you see a ", and then followed by a whitespace. But there isnt a whitespace following it - it will always be a double quote.

Note that when Remon give you the string, he said (<table.*?class=")([^"]*)" . That last " is not a typo.

[rpkamp]

^ what he said