Parsing textfile with citations

Question

The issue is that I’m trying to segment the text file by sentences using php. I currently using the following function:

$results = preg_split('/(?<=[.?!])\s+/', $stringtest, -1, PREG_SPLIT_NO_EMPTY);

The issue is that with sentences like these:

In his book The Symposium, Plato wrote “Those who are halves of a man whole pursue males, and being slices, so to speak, of the male, love men throughout their boyhood, and take pleasure in physical contact with men” (qtd. in Isay 11).

It splits it like this:

[0] In his book The Symposium, Plato wrote “Those who are halves of a man whole pursue males, and being slices, so to speak, of the male, love men throughout their boyhood, and take pleasure in physical contact with men” (qtd. 
[1] in Isay 11).

Another example is:

Dr. Evelyn Hooker, a heterosexual psychologist...

The Dr. part would be an issue.

These texts are all from the MASC corpus for NLP.

Answer 1

You may extend @ndn's solution to achieve what you need. Note that $before_regexes contain a list of known abbreviations, add those that are present in your corpora. I added qtd there.

Then, note that $before_regexes and $after_regexes are paired. I added '/(?:[”’"\'»])\s*\Z/u' / '/\A(?:\(\p{L})/u' pair and marked it as a non-sentence boundary (with the first false in the $is_sentence_boundary array. The regex pair means: find a quotation mark (”’"'»), 0+ whitespaces, and then followed with ( (with \() and any Unicode letter (\p{L}), then there should be no split.

function sentence_split($text) {
    $before_regexes = array('/(?:[”’"\'»])\s*\Z/u',
        '/(?:(?:[\'\"„][\.!?…][\'\"”]\s)|(?:[^\.]\s[A-Z]\.\s)|(?:\b(?:St|Gen|Hon|Prof|Dr|Mr|Ms|Mrs|[JS]r|Col|Maj|Brig|Sgt|Capt|Cmnd|Sen|Rev|Rep|Revd)\.\s)|(?:\b(?:St|Gen|Hon|Prof|Dr|Mr|Ms|Mrs|[JS]r|Col|Maj|Brig|Sgt|Capt|Cmnd|Sen|Rev|Rep|Revd)\.\s[A-Z]\.\s)|(?:\bApr\.\s)|(?:\bAug\.\s)|(?:\bBros\.\s)|(?:\bCo\.\s)|(?:\bCorp\.\s)|(?:\bDec\.\s)|(?:\bDist\.\s)|(?:\bFeb\.\s)|(?:\bInc\.\s)|(?:\bJan\.\s)|(?:\bJul\.\s)|(?:\bJun\.\s)|(?:\bMar\.\s)|(?:\bNov\.\s)|(?:\bOct\.\s)|(?:\bPh\.?D\.\s)|(?:\bSept?\.\s)|(?:\b\p{Lu}\.\p{Lu}\.\s)|(?:\b\p{Lu}\.\s\p{Lu}\.\s)|(?:\bcf\.\s)|(?:\be\.g\.\s)|(?:\besp\.\s)|(?:\bet\b\s\bal\.\s)|(?:\bvs\.\s)|(?:\p{Ps}[!?]+\p{Pe} ))\Z/su',
        '/(?:(?:[\.\s]\p{L}{1,2}\.\s))\Z/su',
        '/(?:(?:[\[\(]*\.\.\.[\]\)]* ))\Z/su',
        '/(?:(?:\b(?:pp|[Vv]iz|i\.?\s*e|[Vvol]|[Rr]col|maj|Lt|[Ff]ig|[Ff]igs|[Vv]iz|[Vv]ols|[Aa]pprox|[Ii]ncl|Pres|[Dd]ept|min|max|[Gg]ovt|lb|ft|c\.?\s*f|vs|qtd)\.\s))\Z/su',
        '/(?:(?:\b[Ee]tc\.\s))\Z/su',
        '/(?:(?:[\.!?…]+\p{Pe} )|(?:[\[\(]*…[\]\)]* ))\Z/su',
        '/(?:(?:\b\p{L}\.))\Z/su',
        '/(?:(?:\b\p{L}\.\s))\Z/su',
        '/(?:(?:\b[Ff]igs?\.\s)|(?:\b[nN]o\.\s))\Z/su',
        '/(?:(?:[\"”\']\s*))\Z/su',
        '/(?:(?:[\.!?…][\x{00BB}\x{2019}\x{201D}\x{203A}\"\'\p{Pe}\x{0002}]*\s)|(?:\r?\n))\Z/su',
        '/(?:(?:[\.!?…][\'\"\x{00BB}\x{2019}\x{201D}\x{203A}\p{Pe}\x{0002}]*))\Z/su',
        '/(?:(?:\s\p{L}[\.!?…]\s))\Z/su');
    $after_regexes = array('/\A(?:\(\p{L})/u',
        '/\A(?:)/su',
        '/\A(?:[\p{N}\p{Ll}])/su',
        '/\A(?:[^\p{Lu}])/su',
        '/\A(?:[^\p{Lu}]|I)/su',
        '/\A(?:[^p{Lu}])/su',
        '/\A(?:\p{Ll})/su',
        '/\A(?:\p{L}\.)/su',
        '/\A(?:\p{L}\.\s)/su',
        '/\A(?:\p{N})/su',
        '/\A(?:\s*\p{Ll})/su',
        '/\A(?:)/su',
        '/\A(?:\p{Lu}[^\p{Lu}])/su',
        '/\A(?:\p{Lu}\p{Ll})/su');
    $is_sentence_boundary = array(false, false, false, false, false, false, false, false, false, false, false, true, true, true);
    $count = 13;

    $sentences = array();
    $sentence = '';
    $before = '';
    $after = substr($text, 0, 10);
    $text = substr($text, 10);

    while($text != '') {
        for($i = 0; $i < $count; $i++) {
            if(preg_match($before_regexes[$i], $before) && preg_match($after_regexes[$i], $after)) {
                if($is_sentence_boundary[$i]) {
                    array_push($sentences, $sentence);
                    $sentence = '';
                }
                break;
            }
        }

        $first_from_text = $text[0];
        $text = substr($text, 1);
        $first_from_after = $after[0];
        $after = substr($after, 1);
        $before .= $first_from_after;
        $sentence .= $first_from_after;
        $after .= $first_from_text;
    }

    if($sentence != '' && $after != '') {
        array_push($sentences, $sentence.$after);
    }

    return $sentences;
}

See the PHP demo.