Month: November 2011

I really can't believe that there isn't any article explaining using regular expression to find a position of a given string. It is very command to use strpos or stripos to find the first occurrences of a given string in PHP. However, problem comes if strpos or stripos gives you the wrong result. Assuming you are looking for the symbol "RM" (Ringgit) on a given text. However, on the given text there exist a word called "RMX9182 is the code for this item selling at RM2000". It is obvious that you want your program to retrieve the symbol on "RM2000" instead of "RMX9182". Using the following strpos or stripos will definitely give you a wrong result.

$text = "RMX9182 is the code for this item selling at RM2000";
$position = stripos($text, "RM"); // return 0

Using the following regular expression, we can use regex to pinpoint the correct symbol pattern we want. In this case,

$text = "RMX9182 is the code for this item selling at RM2000";
$pattern = "/RM\\d/i";
preg_match($pattern, $text, $matches, PREG_OFFSET_CAPTURE);
print_r($matches);

It will print out the following array

Array
(
    [0] => Array
        (
            [0] => RM2
            [1] => 45
        )

)

Notice that the second index, 45, is the index of the found text. Assuming we have more than one matches in our text,

$text = "RMX9182 RM90 is the code for this item selling at RM2000";
$pattern = "/RM\\d/i";
preg_match($pattern, $text, $matches, PREG_OFFSET_CAPTURE);
print_r($matches);

It will still retrieve the first found text as shown below

Array
(
    [0] => Array
        (
            [0] => RM9
            [1] => 8
        )

)

However, if you would like to find all the position on a string, just use preg_match_all instead as shown below,

$text = "RMX9182 RM90 is the code for this item selling at RM2000";
$pattern = "/RM\\d/i";
preg_match_all($pattern, $text, $matches, PREG_OFFSET_CAPTURE);
print_r($matches);

It will gives you a result similar to the one shown below,

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [0] => RM9
                    [1] => 8
                )

            [1] => Array
                (
                    [0] => RM2
                    [1] => 50
                )

        )

)

This may seems very simple and direct but developer often find it easier to just stick to stripos or strpos until things get a bit off. If it's pure string. native methods might be just the right tool for you but if patterns is require, nothing beats regular expression

Today i wanted to extract a particular word or text (if the word doesn't make sense) given a position in a string. I tried to search this for php platform but couldn't really find an answer for it. In facts, i cannot find any through google for such functionality in php. However, i manage to find it on python. It was actually pretty simple and straight forward and i believe most of people will get it in one look. But we don't revamp the wheel so here you go.

      function extractWord($text, $position){
         $words = explode(' ', $text);
         $characters = -1; 
         foreach($words as $word){
            $characters += strlen($word);
            if($characters >= $position){
               return $word;
            }   
         }   
         return ''; 
      }   

pretty easy isn't it? The above will basically split the string into individual word and loop these words and calculate the total position. If the position of the total characters is larger or equal to the position you provide, we have reach the word that we want. Here is a little example on how to extract word from a string given a position.

$text = 'This is an example of how to extract word from a string given a position in php
$position = strpos($text, 'examp');
$word = extractWord($text, $position); // return example

It's pretty simple and straight forward but it does save some time and focus on something more important. Hope it helps 🙂