Replace many instances in single string

[Anon]

Hi 🙂

I am looking for (while developing a large photo database that has extensive decriptions for each photo) an effective way to parse those descriptions and replace certain keywords within the strings with URLs to local files.

(I'm trying to avoid having to manually put URLs into thousands of descriptions).

What I'd like to do would be to maintain a single set (SQL table or array?) of keywords and their URLs, like

Glacier -> /glaciers/info.htm

Is there a better (and faster) way to do this than looping through the string, one keyword at a time using str_replace()? There could be as many as 1-200 keywords that I'd like to parse eventually.

Thanks in advance,
Gudmundur Helgason

[amcgrath]

One idea would be to create a function that parses through the description when you actually display it, and do your replacement then. That way, you don't have to change the actual data in the database (which might not be good, especially if the locations change, the data is used in other way, etc)

[Anon]

Yes, is is precicely what was gonna do 🙂 But I am worried it might be too CPU and time-intensive to do many descriptions.

But I can test this I guess.

The main goal was to own a single file of "approved" links and keywords.

I just am not sure the str_replace() loop (perhaps 1-300 cycles if I replace one word at a time) is the most efficient way to do this.

Gudmundur Helgason

Al McGrath wrote:

One idea would be to create a function that parses through the description when you actually display it, and do your replacement then. That way, you don't have to change the actual data in the database (which might not be good, especially if the locations change, the data is used in other way, etc)

[amcgrath]

Yea, I agree with you about intensity. One other "possible" idea, though a little redundant, would work:

Create another column or table (your preference) that holds the converted data (re: the description with urls included). If the field's there, then display it. If not, then run the function and insert the results... basically, let the user parse the data for you.

Gudmundur Helgason wrote:

Yes, is is precicely what was gonna do 🙂 But I am worried it might be too CPU and time-intensive to do many descriptions.

But I can test this I guess.

The main goal was to own a single file of "approved" links and keywords.

I just am not sure the str_replace() loop (perhaps 1-300 cycles if I replace one word at a time) is the most efficient way to do this.

Gudmundur Helgason

Al McGrath wrote:

One idea would be to create a function that parses through the description when you actually display it, and do your replacement then. That way, you don't have to change the actual data in the database (which might not be good, especially if the locations change, the data is used in other way, etc)

[Anon]

OK, will try that 🙂

Anyhow I've done a test on this and it works very nicely with str_replace() (Have about 35 entries in the replace table so far).

But I'd love to make it only replace the string in question the first time it sees it (i.e. not all instances). Would look a lot nicer like that.

This is the str_replace() version that works nicely:
$new_str = str_replace(" $string", " <a href=\"$link\">$string</a>", "$new_str");

I tried to get this working with preg_replace() but I am unable to get it running. Any ideas?

$new_str2 = preg_replace(' $string', ' <a href=\"$link\">$string</a>', '$new_str', "1");

(I've tried a number of versions of this but I always get some delimitter errors or something 🙂

Regards,
Gudmundur Helgason