我只想知道是否有任何内置的php函数可以在给定的两个关键字（关键字1和关键字2）之间获得子字符串。注意，关键字可能在字符串中重复，所以我必须能够获得xth关键字1和yth关键字2之间的子字符串。此外，我主要使用unicode字符，所以函数应该是独立于字符集的。
请帮我解决这个问题。
这是他们剧院里戴帽子的猫。$keyword1="is"$关键字2="the"；
任务：如何获取上面给定字符串中第二次出现"is"和第三次出现"the"之间的子字符串。
回答："中戴帽子的猫"
您可以使用正则表达式：
$string = "This is their cat with a hat in the theater";
$regex1 = "/.*? is |^is/";
$regex2 = "/ the .*| the$/";
echo preg_replace($regex1, '', preg_replace($regex2, ' the', $string));
EDIT以下是更通用的代码：
function find($text, $str, $offset) {
$len = strlen($text);
$search_len = strlen($str);
$count = 0;
for ($i=0; $i<$len; ++$i) {
if (substr($text, $i, $search_len) == $str) {
if (++$count == $offset) {
return $i;
}
}
}
return -1;
}
function between($text, $word1, $offset1, $word2, $offset2) {
$start = find($text, $word1, $offset1);
$end = find($text, $word2, $offset2);
if ($start != -1 && $end != -1) {
return substr($text, $start + strlen($word1), $end-$start-strlen($word2));
} else {
return '';
}
}
$string = "This is their cat with a hat in the theater";
echo between($string, 'is', 2, 'the', 3);
echo between($string, 'at', 1, 'at', 3);
以下两个函数的组合适用于包括unicode字符在内的任何字符串：
//Gets the position of a given substring with its offset;
function strposOffset($string, $search, $offset)
{
/*** explode the string ***/
$arr = explode($search, $string);
/*** check the search is not out of bounds ***/
switch( $offset )
{
case $offset == 0:
return false;
break;
case $offset > max(array_keys($arr)):
return false;
break;
default:
return mb_strlen(implode($search, array_slice($arr, 0, $offset)), "utf-8");
}
} //Source: www.phpro.org
//Extracts a substring between given two given substrings with their offsets.
function extractMiddleSubstr($string, $substr1, $offset1, $substr2, $offset2){
$strlen_substr1 = mb_strlen($substr1, "utf-8"); //length of substr1;
$strpos_substr1 = strposOffset($string, $substr1, $offset1); //position of substr1;
$strpos_substr2 = strposOffset($string, $substr2, $offset2); //position of substr2;
if($strpos_substr1!==null && $strpos_substr2!==null && $strpos_substr1!==false && $strpos_substr2!==false){
if($strpos_substr1<=$strpos_substr2){
$strpos_substr = $strlen_substr1+$strpos_substr1; //position of substr;
$strlen_substr = $strpos_substr2-$strpos_substr; //length of substr;
$substr = mb_substr($string, $strpos_substr, $strlen_substr, "utf-8"); //substr;
$substr = trim($substr); // removes whitespaces;
return $substr;
}else{
return false;
}
}else{
return false;
}
}