How Can I Efficiently Match Quoted Strings in PHP, Ignoring Escaped Quotes?

PHP: Matching Strings While Ignoring Escaped Quotes Within Quotes

To match strings enclosed within both single (') and double (") quotes, you can use the following regular expressions:

<br>$code = preg_replace_callback( '/"(.*?)"/', array( &$this, '_getPHPString' ), $code );</p>
<p>$code = preg_replace_callback( "#'(.*?)'#", array( &$this, '_getPHPString' ), $code );<br>

However, these expressions do not account for escaped quotes within the strings. To ignore escaped quotes, you can use more sophisticated regular expressions:

Good (But Inefficient):

<br>"(<sup><a href="https://www.php.cn/link/d58f36f7679f85784d8b010ff248f898" rel="nofollow" target="_blank">1</a></sup>|.)*"<br>

Better (More Efficient with Special Quantifiers):

<br>"(<sup><a href="https://www.php.cn/link/960fe54b16d890a75e845fcd23afc32d" rel="nofollow" target="_blank">2</a></sup>  |.)*"<br>

Best (Most Efficient with Unrolled Loop):

<br><sup><a href="https://www.php.cn/link/84fec9a8e45846340fdf5c7c9f7ed66c" rel="nofollow" target="_blank">3</a></sup><em>(?:.<sup><a href="https://www.php.cn/link/9b1cab1b93285ce58e7c1dc576ff8a14" rel="nofollow" target="_blank">4</a></sup></em>)*<br>

These improved expressions will allow escaped quotes (' and ") to be ignored within their respective quoted strings. For PHP syntax, use the following:

<br>$re_dq = '/"<sup><a href="https://www.php.cn/link/b594f8f8fcc3cc7910e2dcd4269a2e95" rel="nofollow" target="_blank">5</a></sup><em>(?:\.<sup><a href="https://www.php.cn/link/096ce33c96792e289516407eb29b62bb" rel="nofollow" target="_blank">6</a></sup></em>)*"/s';<br>$re_sq = "/'<sup><a href="https://www.php.cn/link/57947ed4d4130c7ff0a057c8654dd1a3" rel="nofollow" target="_blank">7</a></sup><em>(?:\.<sup><a href="https://www.php.cn/link/7835a9ef21ac8378a23835829594d598" rel="nofollow" target="_blank">8</a></sup></em>)*'/s";<br>

These regular expressions provide accurate and efficient matching of strings, even when dealing with escaped quotes.

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1. " ↩
2. " ↩
3. " ↩
4. " ↩
5. "\ ↩
6. "\ ↩
7. '\ ↩
8. '\ ↩

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