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Date: Wed, 7 Jun 2017 22:13:34 +0200
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To: Rasmus Schultz <rasmus@mindplay.dk>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] preg_match() option for anchored offset?
From: nikita.ppv@gmail.com (Nikita Popov)

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On Wed, Jun 7, 2017 at 10:03 PM, Rasmus Schultz <rasmus@mindplay.dk> wrote:

> What do you think about adding another option to preg_match() to allow the
> $offset parameter to be treated as the start anchor?
>
> The manual proposes to do this:
>
>     $subject = "abcdef";
>     $pattern = '/^def/';
>     $offset = 3;
>     preg_match($pattern, substr($subject, $offset), $matches);
>
> In other words, use substr() to copy the entire remainder of the string.
>
> I just wrote a simple SQL parser tonight, and had to use this approach,
> which (I imagine) must be pretty inefficient?
>
> I'd like to be able to do the following:
>
>     $subject = "abcdef";
>     $pattern = '/^def/';
>     $offset = 3;
>     preg_match($pattern, $subject, $matches, PREG_ANCHOR_OFFSET, $offset);
>
> This new option would make the ^ anchor work from the given $offset, which
> allows me to parse the entire $subject without copying anything.
>
> Thoughts?
>

You are looking for the \G anchor or the A modifier.

Nikita

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