How replace some text in a paragraph with other text in PHP

Question

<?php

$string="Hello how are ##you ? I want ##join you.";

echo $string;

// now I want replace all ##.... words with <a>##.....</a>
// example Hello how are <a>##you</a> ? I want <a>##join</a>you.

?>

Now I want replace all ##.... words with ##..... example Hello how are ##you ? I want ##join you.

Answer 1

I'll let others go for regex solutions. I'll propose something that hopefully more readable.

The following code uses my Parser class from Paladio (it's under CC-BY 3.0), it works on UTF-8.

The code is explained in the comments:

<?php
    $string = "Hello how are ##you ? I want ##join you.";

    // now I want replace all ##.... words with <a>##.....</a>

    //Create a parser object for the string
    $parser = new Parser($string);

    //Create a variable to hold the result
    $result = '';

    //While we haven't reached the end of the string
    while($parser->CanConsume())
    {
        //Take all the text until the next '##' or the end of the string
        // and add to the result the string taken
        $result .= $parser->ConsumeUntil('##');
        //If we take a '##'
        if ($parser->Consume('##'))
        {
            //Take the text until the next whitespace or new line
            $tag = $parser->ConsumeUntil(array(' ', "\t", "\r", "\n"));
            //Add the new converted text to the result
            $result .= '<a>###'.$tag.'</a>';
        }
    }

    // example Hello how are <a>##you</a> ? I want <a>##join</a>you.
    echo $result;
?>

---

Based on the comments, this is a modified version that will allow to detect words marked with any of the given strings ('##' and '**' in the example):

function autolink($ptext, $detc)
{
    // declared whitespace for readability and performance
    $whitespace = array(' ', "\t", "\r", "\n");
    $parser = new Parser($ptext);
    $result = '';
    while($parser->CanConsume())
    {
        $result .= $parser->ConsumeUntil($detc);
        if ($parser->Consume($detc))
        {
            $newtag = $parser->ConsumeUntil($whitespace);
            $result .= '<a href='.$newtag.'>'.$newtag.'</a>';
        }
    }
    return $result;
}

Example usage:

echo autolink("Hello how are ##you ? I want **join you.", array('##', '**'));

Outputs:

Hello how are <a href=you>you</a> ? I want <a href=join>join</a> you.

Tested on my local server.

---

Notes:

1. The instruction $parser->Consume($detc) will return the found string, so you can use it to branch, example:

   $input = $parser->Consume(array('a', 'b')); if ($input === 'a') { // do something } else if ($input === 'b') { // do something else } else /if ($input === null)/ { // fallback case }

2. The supported things to Consume are:

1. Given strings.
2. Arrays of strings.
3. Numbers (amount of characters).
4. Null (will consume a single character).

3. Parser uses mb_* functions for some of the operations^, and expects UTF-8. If you experience problems with encoding you want to call mb_internal_encoding('UTF-8'); before using Parser and convert your string to UTF-8 (I recommend iconv for this operation). ^: Some other parts are optimized using byte per byte operations.