Tag Archives: Snippet

PHP: Tail tackling large files

Needed a function that could get me the last N lines of a log file. Wanted it to be efficient and not dependent on anything other than my code.

Found some versions, but they were either a bit messy or depended on unstable arithmetic (where filesize is greater than PHP_INT_MAX). So, I decided to take on the challenge and try to write one myself. Nice little exercise 🙂

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Java: How to deal with the BOM in a Unicode InputStream

Ok, so I was happily reading CSV files from an SFTP server. The file content is returned as an InputStream and I I used a BufferedReader to read it line by line. Each line contained either a header or an order. The header lines started with the string “HDR”.

However, I suddenly discovered that my code was consistently skipping the first header (and as a result the orders belonging to it). The reason, I found, was simple. The first header, on the first line, didn’t start with “HDR”, it started with “â–¡HDR”! And that undisplayable square turned out to be a Unicode Byte Order Mark (BOM).

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PHP: How to get all images from an HTML page

I was curious to how I could make something similar to what Facebook does when you add a link. Somehow it loads images found on the page your link leads to, and then it presents them to you so you can select one you want to use as a thumbnail.

Well, step one to solve this is of course to find all the images on a page, and that is what I will present in this post. It will be sort of like a backend service we can use later from an AJAX call. You post it a URL, and you get all the image URLs it found back. Let’s put the petal to medal!

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PHP: Dealing with absolute and relative URLs

I’m currently writing a post on how to get image tags from a remote HTML page using PHP. One sticky issue with that is that the image URLs you find is a joyful mix of absolute and relative URLs.

Luckily, I found a function on nashruddin.com which seem to handle them alright. After a bit of clean up and fixing an error, we have this function:

function make_absolute($url, $base)
    // Return base if no url
    if( ! $url) return $base;

    // Return if already absolute URL
    if(parse_url($url, PHP_URL_SCHEME) != '') return $url;
    // Urls only containing query or anchor
    if($url[0] == '#' || $url[0] == '?') return $base.$url;
    // Parse base URL and convert to local variables: $scheme, $host, $path

    // If no path, use /
    if( ! isset($path)) $path = '/';
    // Remove non-directory element from path
    $path = preg_replace('#/[^/]*$#', '', $path);
    // Destroy path if relative url points to root
    if($url[0] == '/') $path = '';
    // Dirty absolute URL
    $abs = "$host$path/$url";
    // Replace '//' or '/./' or '/foo/../' with '/'
    $re = array('#(/\.?/)#', '#/(?!\.\.)[^/]+/\.\./#');
    for($n = 1; $n > 0; $abs = preg_replace($re, '/', $abs, -1, $n)) {}
    // Absolute URL is ready!
    return $scheme.'://'.$abs;

I can sort of read through and see what it does, but I can’t explain it very well. So, I’ll just leave it at that. So far it has worked fine for me. Maybe some corner cases that are missing, and if there are, please let me know!

💡 What I added to the original function was line 5 and 17. The first to prevent it from crashing if the url is null or empty, and the second to prevent it from crashing if parse_url finds no path. For example if the url is http://www.example.com (No /whatever at the end).

The base tag

A tag that is easy to forget about is the base tag. The above function gets the base path from the URL given as base. For example if you gave it http://www.example.com/directory/file.html as base, it would use http://www.example.com/directory/. However, if file.html included the following base tag:

<base href="http://www.example.com/">

Then the base path would be http://www.example.com/ instead. Fun, eh?

As long as you know about it, it’s not to hard to deal with though. You just need to get a hold of it and provide that as base instead when using the function above.

Works On My Machineâ„¢! And if it doesn’t on yours, let me know. If it’s a mistake in the function, I’d like to fix it!

How to search for a table or column in a big Oracle database

I needed to find columns containing a certain string. That is, the name of the column should contain that string. Actually not too difficult to do 🙂

SELECT owner, TABLE_NAME, column_name
FROM all_tab_columns
WHERE column_name LIKE '%FOO_ID%';

That gives you a nice list of all columns containing FOO_ID and what tables you find them in. Fantastic! Now, back to work…