所以基本上，我只是想在一个字符串中搜索一个字符串。
虽然，它比这有点棘手。
我有三个小字符串one，，，，twothree
而且我有一个大字符串，它被保存为一个变量并且很长..实际上有几段长。
我需要创建一个函数，让我查看哪个字符串首先出现。
例如，这样的字符串：
Hello, testing testing one test some more two
将返回one，因为它之前发生过two。
另一个例子：
Test a paragraph three and testing some more one test test two
将返回three，因为它发生在one和之前two。
有人对如何做到这一点有任何建议或例子吗？对 PHP 来说非常新，不知道如何去做。谢谢！
preg_match()与一个简单的交替使用：
if (preg_match('/one|two|three/', $string, $matches)) {
echo $matches[0];
}
结果：
Hello, testing testing one test some more two
-> one
Test a paragraph three and testing some more one test test two
-> three
如果你也需要这个位置，你可以添加一个标志：
if (preg_match('/one|two|three/', $string, $matches, PREG_OFFSET_CAPTURE)) {
echo 'Found ' . $matches[0][0] . ' @ ' . $matches[0][1];
}
作为一个函数：
function findFirst($string, array $needles)
{
$pattern = '/' . join('|', array_map(function($str) {
return preg_quote($str, '/');
}, $needles)) . '/';
if (preg_match($pattern, $string, $matches)) {
return $matches[0];
} else {
return false;
}
}
要使用：
echo findFirst($string, array('one', 'two', 'three'));
见http://www.php.net/manual/en/function.strpos.php
就像
$longString = "Hello, testing testing one test some more two";
$onePosition = strpos($longString, "one");
$twoPosition = strpos($longString, "two");
$threePosition = strpos($longString, "three");
$onePosition; // 23
$twoPosition; // 42
$threePosition; // -1
然后你只需比较每个变量以找到最低的。笨重，但对于 3 个变量来说工作量不大。
这应该有效：
<?php
$arrWords = array("one", "two", "three");
$strInput = "Test a paragraph three and testing some more one test test two";
function getFirstOccurrence($strInput, $arrWords) {
$arrInput = explode(" ", $strInput);
foreach($arrInput as $strInput) {
if(in_array($strInput, $arrWords)) {
return $strInput;
}
}
return null;
}
print "First word is: " . getFirstOccurrence($strInput, $arrWords);
?>
这是一个示例算法：
function getFirstWord(array $needles, $haystack) {
$best = null; //the best position
$first = null; //the first word
foreach($needles as $needle) {
$pos = strpos($haystack, $needle);
if($pos !== false) {
if($best === null || $pos < $best) {
$best = $pos;
$first = $needle;
}
}
}
//returns the first word, or null if none of $needles found
return $first;
}
$needles = array('one', 'two', 'three');
echo getFirstWord($needles, 'Hello, testing testing one test some more two'); // one
echo getFirstWord($needles, 'Test a paragraph three and testing some more one test test two'); // three
最佳解决方案将最小化 $haystack 上的迭代。您可以从字符串的开头开始，每次前进一个字符时，查找从当前位置开始的任何 $needles。一旦你找到一个，宾果游戏。
尝试这样的事情：
$string = 'Hello, testing testing one test some more two';
$words = Array("one", "two", "three");
$low_pos = strlen($string);
$first = '';
foreach($words as $word)
{
$pos = strpos($string, $word);
echo "Found ".$word." at ".$pos."<br />";
if($pos !== false && $pos < $low_pos)
{
$low_pos = $pos;
$first = $word;
}
}
echo $string."<br />";
echo "FIRST: ".$first;
输出：
Found one at 23
Found two at 42
Found three at
Hello, testing testing one test some more two
FIRST: one
如果你想变得花哨，你可以使用带有 array_map、array_filter、array_search 和 min 的闭包。
function whichFirst(array $list, $string){
// get a list of the positions of each word
$positions = array_map(function($val) use ($string){
return strpos($string, $val);
}, $list);
// remove all of the unfound words (where strpos returns false)
$positions = array_filter($positions, function ($x){ return $x !== false; });
// get the value with the key matching the lowest position.
$key = array_search(min($positions), $positions);
return $list[$key];
}
例子：
$str = "Hello, testing testing one test some more two";
$list = ["one","two","three"];
echo whichFirst($list, $str);
// outputs one