如何使用php在字符串中找到以特定leter或元素开头的单词？

Question

我正在使用str_word_count()来计算一个单词在文本中出现的次数，但我真正想要的是只计算以'[word here]'开头和结尾的特定单词

$text = "Degree binb 'Information-Systems', 'Computer-Science' , or other KM-relevant field required; graduate degree preferred.";

$words = str_word_count($text, 1); 
$frequency = array_count_values($words);
arsort($frequency);
echo '<pre>';
print_r($frequency);
echo '</pre>';

输出：

Array
(
    [required] => 1
    [field] => 1
    [graduate] => 1
    [degree] => 1
    [preferred] => 1
    [KM-relevant] => 1
    [other] => 1
    [binb] => 1
    ['Information-Systems'] => 1
    ['Computer-Science'] => 1
    [or] => 1
    [Degree] => 1
)

Answer 1

若要查找单引号中的所有单词，请在preg_match_all()中使用正则表达式

$text = "Degree binb 'Information-Systems', 'Computer-Science' , or other KM-relevant field required; graduate degree preferred.";

preg_match_all("/'([^']+)'/", $text, $matches);

var_dump($matches[1]);
echo "Found " . count($matches[1]) . " matches." . PHP_EOL;

这将产生以下结果：

array(2) {
  [0] =>
  string(19) "Information-Systems"
  [1] =>
  string(16) "Computer-Science"
}
Found 2 matches.

Answer 2

使用substr()检查字符串的起始/结束是否等于其他字符串，您正在搜索：

http://php.net/manual/en/function.substr.php

正如您可以注意到的，如果您想从字符串的末尾进行比较，请使用负$start值。

对于长度参数，使用strlen()获取字符串长度：

http://php.net/manual/en/function.strlen.php

Answer 3

PHP伪代码示例：

function find_words_prefix($text, $prefix)
{
  $words = array_filter(explode(' ', $text), 'strlen'); // get only non-emoty words
  $prefixed_words = array();
  $prefix_len = strlen($prefix);
 foreach ($words as $word)
{
if (strlen($word) < $prefix_len) continue; // no use testing this word as it is smaller than prefix
if ( 0 === strpos($word, $prefix) ) $prefixed_words[] = $word;
}
return $prefixed_words;
}

像这样使用：

$prefixed_words = find_words_prefix("Degree binb 'Information-Systems', 'Computer-Science' , or other KM-relevant field required; graduate degree preferred.", "D");

print_r($prefixed_words);

类似的函数可以用于后置词。