Split Paragraphs into Shorter Paragraphs in PHP

Here is a PHP function to split a large paragraph into shorter paragraphs. Paragraphs that are too large are those that have more than 4 sentences. This will count the sentences in a paragraph, and if needed, convert it into shorter paragraphs.

You need all of the 4 following functions for this. Below this code, you’ll find some examples of how to use this.

/**
 * Break paragraph into shorter paragraphs
 * @param string $p the paragraph to break up
 * @return mixed String of shorter paragraphs, or false if paragraphs was already less than 5 sentences. Returned string will have max 4 sentences per paragraph.
 */
function shorter_paragraphs($p) {
	$buffer = '';
   
    do {
    	$p_in = $p;
    	$c = count_sentences($p_in);

    	$replace = true;
   
        if ($c > 4) {
        	$n_arr = get_n($c);
        	$n = $n_arr[0];
        	$more = $n_arr[1];
	        $s = get_sentences($p_in, $n);
	        $s = trim($s);
	        $buffer .= $s . PHP_EOL . PHP_EOL;
	        $p_in = str_replace($s, '', $p_in);

	        if (1 === $more) {
	            $c = count_sentences($p_in);
	        } else {
	            $buffer .= trim($p_in);
	            $c = 0;// kill loop
	        }

        } else {

        	$buffer .= trim($p_in);
        	$c = 0;// kill loop
			
			if (trim($buffer) == trim($p_in)) {
				$replace = false;
			}
        }

        $p = $p_in;

    } while ($c > 4);

    if ($replace) {
		return $buffer;
    } else {
    	return false;
    }

}

function count_sentences($str){
    return preg_match_all('/[^\s](\.|\!|\?)/',$str,$match);
}

/**
 * Get the first $n sentences in a string.
 * @param int $n The number of sentences to get
 * @return string The sentences
 */
function get_sentences($string, $n) {
    $split = preg_split('/(\.|\!|\?)/', $string, $n + 1, PREG_SPLIT_DELIM_CAPTURE);
    $sentences = implode('', array_slice($split, 0, 2 * $n));
    return $sentences;
}

/**
 * Get number of paragraphs to take off the top based on total
 * number of sentences in original paragraph.
 * @param int $c The total count of sentences in original paragraph
 * @return array
 */
function get_n($c) {
	switch ($c) {
	    case 6:
	    case 8:
	        $n = $c / 2;
	        $do_more = 0;
	        break;
	    case 5:
	    case 7:
	        $n = 3;
	        $do_more = 0;
	        break;
	    case 9:
	    case 12:
	    case 15:
	        $n = 3;
	        $do_more = 1;
	        break;
	    case 10:
	    case 11:
	    case 13:
	    case 14:
	    case 16:
	        $n = 4;
	        $do_more = 1;
	        break;
		default:
			$n = 0;
			$do_more = 0;
	}
	return array($n, $do_more);
}

Examples

1. Convert a string of text into short paragraphs of a maximum of four sentences each.

   $p = ( $new_paragraphs = shorter_paragraphs($string) ) ? $new_paragraphs : $string;

2. Check a whole body of text with existing paragraphs, and split any paragraphs with more than 4 sentences into shorter paragraphs.

   This will return the entire original text, but all paragraphs will have a maximum of 4 sentences. The $out variable will hold the final text.

   $out = $original_text;
   $original_text = trim($original_text);
   
   // split into paragraphs
   
   $paragraphs_array = preg_split('#(\r\n?|\n)+#', $original_text);
   
   // check each paragraph for length
   
   foreach ($paragraphs_array as $p) {
   	$p = trim($p);
   	if ($p) {
   		$new_ps = shorter_paragraphs($p);
   		if ( $new_ps ) {
   
   			// replace this paragraph with split shorter ones
   			$out = str_replace($p, $new_ps, $out);
   		}
   
   	}
   }
   
   // The $out variable holds the final text
   

The count_sentences() function is the most expensive one here.