preg_match error: Compilation failed: missing terminating ] for character class

Question

I've got a series of .txt files that I'm reading in a for loop. And I've placed a token in some of the text files in the form [widget_]

So, the entire contents of the text file might be [widget_search] for example. And another text file might contain the content [widget_recent-posts]. Others might just have html formatted text and not have the token at all.

In the for loop, I'm doing a preg_match to see if the text file is one in which the contents matches my token pattern. And if a match, I'm executing some conditional code.

However, I'm getting an error when I run a trace test to see if there's a match.

The error is:

Warning: preg_match() [function.preg-match]: Compilation failed: missing terminating ] for character class at offset 8 in C:\xampplite\htdocs\test\wp-content\plugins\widget-test\widget-test.php on line 227

And here's the code at line 227:

if (preg_match("/[widget_/i",$widget_text)) {//do something}

Answer 1

You should escape the [ character like this:

if (preg_match("/\[widget_/i",$widget_text)) { // do something }

Answer 2

it much cleaner to use preg_quote like this:

if (preg_match(preg_quote("/[widget_/i"),$widget_text)) {//do something}