This function comes in handy when collecting information about a user’s browser to determine the content capabilities for that user. It returns an associative array containing information such as the browser type, version, whether or not it is capable of handling frames, cookies, and javascript, and the platform on which the browser is running.
This kind of information could prove to be invaluable when tracking users, logging site usage, or building a statistics engine for your site.
Ever needed to split up a URL into its individual components to extract data from it? Look no further than parse_url(). This function does all the dirty work of determining what is what in the URL and conveniently presents it to you in an associative array. The resulting array will contain one or more elements of the URL. Take the following URL for example:
http://www.domain.com/controller.php?var=value&another=value2#anchor
Passing this URL string to parse_url() would generate an array like the following:
Array
(
[scheme] => http
[host] => www.domain.com
[path] => /controller.php
[query] => var=value&another=value2
[fragment] => anchor
)
Don’t worry if the URL isn’t perfectly formed — parse_url() will do it’s best to extract whatever information it possibly can from the string passed to it.
This function does exactly what it says: it parses a string of HTML and extracts the meta tags from it. The results are returned in an associative array with the name attributes as the keys and the value attributes as the values.
This could be used to extract meta information such as keywords and descriptions from pages in any sort of PHP-based web crawler.
Filtering arrays in PHP is easy thanks to array_filter(). Let’s say you wanted to filter the following array of integers for any numbers less than 5:
$array = array(1, 11, 56, 3, 3, 633, 34, 2, 18, 9);
A classic way to approach this task would be to use a loop to examine each element and selectively generate a filtered array:
foreach( $array as $num ) {
$filtered_array = array();
if( $num < 5 ) {
$filtered_array[] = $num;
}
return $filtered_array;
}
However, there’s an easier way to accomplish this. Let’s define a function that checks a number for our filter condition (which, by the way, makes it easier to change/reuse later on):
function filter( $item ) {
return $item < 5;
}
And now, generating the filtered integer array is a simple one-line task:
$filtered_array = array_filter($array, 'filter');
The resulting array looks like this:
Array
(
[0] = 1
[3] = 3
[4] = 3
[7] = 2
)
This function converts a string representation of a number in one format (radix) to a string representation of that same number in another format, up to and including base 36. The most common use for this is to convert between decimal and hexadecimal, but there are many other potential uses depending on the scope of your application.
$numBase10 = 4567;
$numBase16 = base_convert($numBase10, 10, 16);
echo $numBase16;
$numBase2 = base_convert($numBase16, 16, 2);
echo $numBase2;
Results:
11d7
1000111010111
The use of globally-unique identifiers, or GUIDs, is becoming increasingly more widespread. PHP’s on top of things and provides this function to generate them for your applications. The two optional arguments allow you to specify a prefix for the identifier and whether or not to add more entropy to the end.
echo uniqid();
echo uniqid('prefix');
echo uniqid('', true);
echo uniqid('prefix', true);
Results:
48c88453d9702
prefix48c88453d970e
48c88453d97100.75111063
prefix48c88453d97130.65378524
The Levenshtein distance between two strings is the minimum number of characters in one string that must be altered, added, or removed in order to end up with the second string. For example, take the words cat and car. The Levenshtein distance between the two words is 1, since to go from cat to car, the only change required is to replace the “t” with an “r”.
The levenshtein() PHP function finds this distance. Pass it two strings, and it returns the minimum distance, or number of required changes to go from the first string argument to the second one. Here’s an few examples:
$lev_dist = levenshtein('tothbrush', 'toothbrush');
echo $lev_dist;
$lev_dist = levenshtein('car', 'truck');
echo $lev_dist;
$lev_dist = levenshtein('undergraduate', 'graduate');
echo $lev_dist;
Results:
1
5
5
This can be particularly useful for catching and correcting spelling errors in user input, especially when dealing with search terms. I’d be interested to see other clever uses for this that people come up with. Note that there is a 255 character limit imposed on the strings used as arguments to the function, but several variations of this function without the imposed limit have been posted on PHP.net.
Pack() works similarly to sprintf(), but rather than returning an ordinary string, pack() returns a binary string. This can be incredibly useful when writing custom serialization routines or when sending raw, protocol-specific data to a host.
As an example, let’s construct a data packet consisting of two short integers, followed by a character:
$sint_1 = 42;
$sint_2 = 11;
$my_char = 'x';
$bin_str = pack('nnC', $sint_1, $sint_2, $my_char);
The resulting binary string will contain the following bytes:
0x00 0x1A 0x00 0x0B 0x78
The list of acceptable format characters includes individual characters for specifying byte order in integers as well, another reason why this can become handy when dealing with network applications.
The soundex key of a string provides information about how that string is pronounced. The function will generate a soundex key for a word, which then can be used when searching for similar sounding words. This is especially useful when searching a database.
echo soundex('stake');
echo soundex('steak');
echo soundex('milk');
echo soundex('mill');
Results:
S320
S320
M420
M400
If you’re only dealing with words in the English language, you may prefer to use metaphone() instead, which uses a better understanding of English word pronunciation and is thus more accurate.
Given a specified day (and, optionally, a locale), this function will return the time at which the sun will set.
The first thing that came to mind when I heard about this function was the ability to swap stylesheets based on the time of day at which a visitor visits a website. For example, this function could be used to create a simple system that displays a daytime theme to the visitor if the sun is still up in their area, and a nighttime theme once the sun has set.
echo "The sun sets at " . date_sunset(time(), SUNFUNCS_RET_STRING);
Other potential uses for this function include disabling various website functionality based on the time of the sunset (for whatever reason) and tracking daytime versus nighttime visitors.
There are obviously plenty of other interesting PHP functions out there. If you know of any other unique, noteworthy built-in PHP functions, I’d love to hear about them.
