Advanced first and last sentence functions - php

Question

I'm trying to retrieve the first and last sentences from database text entries.
The code I have works fine in this example:
$text = "He was doing ok so far, but this one had stumped him. He was a bit lost..."
The functions:
function first_sentence($content) {
$pos = strpos($content, '.');
if($pos === false) {
return $content;
}
else {
return substr($content, 0, $pos+1);
}
} // end function
// Get the last sentence
function last_sentence($content) {
$content = array_pop(array_filter(explode('.', $content), 'trim'));
return $content;
} // end function
The last sentence function takes into account any trailing...'s at the end of a sentence, but neither can cope with the following:
$text = "Dr. Know-all was a coding master, he knew everything and was reputed the world over. But the Dr. was in trouble..."
Result:
First sentence: Dr.
Last sentence: was in trouble
I need to modify the functions to take into account things like 'Dr.' and other such abbreviations if that's possible, so the last text variable would come out as:
First sentence: Dr. Know-all was a coding master, he knew everything and was reputed the world over
Last sentence: But the Dr. was in trouble
Can it be done? Any help much appreciated!

Answer 1

You can exclude some word by replacing them.
<?
function first_sentence($content) {
$pos = strpos($content, '.');
if($pos === false) {
return $content;
}
else {
return substr($content, 0, $pos+1);
}
} // end function
// Get the last sentence
function last_sentence($content) {
$content = array_pop(array_filter(explode('.', $content), 'trim'));
return $content;
} // end function
$text = "Dr. Know-all was a coding master, he knew everything and was reputed the world over. But the Dr. was in trouble...";
$tmp = str_replace("Dr.","Dr____",$text);
echo $tmm ."\n";
echo str_replace("Dr____","Dr.",first_sentence($tmp ))."\n";
echo str_replace("Dr____","Dr.",last_sentence($tmp ));
?>
WORKING CODE

Answer 2

Maybe you thought about that..
Can you make a function to encode/decode the $content before you search for the sentences;
function encode_content($content){
return $encoded_content = str_replace("Dr.", "Dr#;#", $content);
}
And after you retrieve the sentences, decode again:
function decode_content($content){
return $encoded_content = str_replace("Dr#;#", "Dr." , $content);
}

Answer 3

You can check your substr length, and return only if it is longer than 3 characters (point included). If it is less or equal, you can use a whitelist in order not to stumble upon words such as "No", "Me", "Us", "Oh"... Scrabble dictionaries should be able to help you there :)

Answer 4

Just to answer my own question after putting some new functions together given the answers so far
function encode_text($content){
$search = array("Dr.", "i.e.", "Mr.", "Mrs.", "Ms."); // put our potential problems in an array
$replace = array("Dr#;#", "i#e#", "Mr#;#", "Mrs#;#", "Ms#;#"); // make them good for first and last sentence functions
$encoded_content = str_replace($search, $replace, $content);
return $encoded_content;
} // end encode
Then we just swap the search and replace variables around to make our decode function. Now they can be used with the first and last sentence functions above, and it works a charm. Adding stuff to the arrays is simple, thinking of what's appropriate to add tho is less so :)
Cheers!