正则表达式仅在其他两个特定字符串之间查找特定字符串

Question

Basically, I need to replace the css class alert in about 3000 documents because it breaks bootstrap css. I can find the entire css class by searching (?<=class=")(.*)(?=") , but I can't just find the alert class by using (?<=class=".*)(alert)(?=.*") or anything like that.

Basically, given a set of data:

<div class=" big alert solid">Alert alert</div>
<div class="alert solid">Alert alert</div>
<div class=" big solid">Alert alert</div>

I only want to find the text alert inside the class attribute.

I have a feeling if there is a working solution for this it will involve optional wildcards in the look ahead/behind. Something like:

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

Answer 1

You can try expression like this:

(?<=class\s?=\s?")(.*?)alert(.*?)(?=")

and replacement placeholder then will be like

$1$2

resulting in

<div class=" big  solid">Alert alert</div>
<div class=" solid">Alert alert</div>
<div class=" big solid">Alert alert</div>

Answer 2

Regular expression for any tag eg div , span and p :

(<[A-Z][A-Z0-9]*\b[^>]*\bclass\s*=\s*"(?:|[^"]+))\balert\b((?:|[^"]+)")

Regular expression for just div tags:

(<div\b[^>]*\bclass\s*=\s*"(?:|[^"]+))\balert\b((?:|[^"]+)")

As a replacement choose one of the following:

Replace alert with alternative-alert-class-name :

$1alternative-alert-class-name$2

Or replace alert with nothing:

$1$2

PHP code (note the use of case insensitivity):

$result = preg_replace('/(<[A-Z][A-Z0-9]*\b[^>]*\bclass\s*=\s*"(?:|[^"]+))\balert\b((?:|[^"]+)")/imx', '$1alternative-alert-class-name$2', $subject);

Example input:

<div class="alert">Alert alert</div>
<div class="alert solid">Alert alert</div>
<div class = "alert solid">Alert alert</div>
<div class=" big alert solid">Alert alert</div>
<div class = " big alert solid">Alert alert</div>
<div something="xx" class = " big alert solid">Alert alert</div>
<span enabled something="xx" class = " big alert solid">Alert alert</span>
<div class=" big solid">Alert alert</div>

Example output:

<div class="alternative-alert-class-name">Alert alert</div>
<div class="alternative-alert-class-name solid">Alert alert</div>
<div class = "alternative-alert-class-name solid">Alert alert</div>
<div class=" big alternative-alert-class-name solid">Alert alert</div>
<div class = " big alternative-alert-class-name solid">Alert alert</div>
<div something="xx" class = " big alternative-alert-class-name solid">Alert alert</div>
<span enabled something="xx" class = " big alternative-alert-class-name solid">Alert alert</span>
<div class=" big solid">Alert alert</div>

Answer 3

You can use this:

$data = <<<EOD
<div class=" big alert solid">Alert alert</div>
<div class = "other-alert-class solid">Alert alert</div>
<div class=" big solid">Alert alert</div>
<div class=' big alert solid'>Alert alert</div>
<div class  =  alert>Alert alert</div>
EOD;

$pattern = '~\sclass\s*=\s*(?>["\'](?>[^"\'a]++|(?<=\B|-)a|a(?!lert\b[^-]))*)?\Kalert\b~';

$result = preg_replace($pattern, 'otherclass', $data);