Simple.

Take the text of the article as a string, crop the string to a certain size, append "......" to the string and display it.

<?php

/*################################################################
#                                                                #
# You pass the script a string, a length you want the string     #
# to be and the trailing characters, what the function does,     #
# is takes the string, finds the last word that will fit into    #
# the overall length, and return a string that has been cropped. #
# The function makes sure that a word is not cut in half.        #
#                                                                #
##################################################################
#        Written by David Speake - david@evilwarus.com           #
#      Adapted from Oliver Southgate's ASP interpretation        #
#     http://www.haneng.com/code/VBScript/CropSentence.txt       #
##################################################################
#                                                                #
# Examples:                                                      #
#                                                                #
# $strTemp = "Hello, I am a fish and you are not.";              #
# $strTemp = CropSentence($strTemp, 16, "...");                  #
# //returns "Hello, I am a..."                                   #
#                                                                #
# $strTemp = "Hello, I am a fish and you are not.";              #
# $strTemp = CropSentence($strTemp, 17, "...");                  #
# //returns "Hello, I am a fish..."                              #
#                                                                #
################################################################*/

function CropSentence ($strText, $intLength, $strTrail) 
{
    $wsCount = 0;
    $intTempSize = 0;
    $intTotalLen = 0;
    $intLength = $intLength - strlen($strTrail);
    $strTemp = "";

    if (strlen($strText) > $intLength) {
        $arrTemp = explode(" ", $strText);
        foreach ($arrTemp as $x) {
            if (strlen($strTemp) <= $intLength) $strTemp .= " " . $x;
        }
        $CropSentence = $strTemp . $strTrail;
    } else {
        $CropSentence = $strText;
    }

    return $CropSentence;
}

$strTemp = "Hello, I am a fish and you are not.";
$strTemp = CropSentence($strTemp, 16, "..."); 
print $strTemp;
?>

Thanks FireNet,
As it happens, I found a much simpler way to achieve what I desired, which was to show a teaser when a forum link was rolled over(as here on daniweb).
I used the following code in the title parameter of the topic's (a href) tag, $message being the text I wanted to truncate. It works.

title="<?php echo substr($message, 0, 100); ?>"

I'd like to add a thankyou to all contributors to daniweb. You've helped me enormously with my project, which I hope to complete in the next week or two.

Best Regards,
Taffd

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