正则表达式检查两个第一个单词是否相同

Question

例如:

$s1 = "Test Test the rest of string"
$s2 = "Test the rest of string"

我想积极匹配,$s1但不是$s2,因为第一个词$s1与第二个相同.Word 'Test'就是例子,正则表达式应该适用于任何单词.

Answer 1

if(preg_match('/^(\w+)\s+\1\b/',$input)) {
  // $input has same first two words.
}

说明:

^    : Start anchor
(    : Start of capturing group
 \w+ : A word
)    : End of capturing group
\s+  : One or more whitespace
\1   : Back reference to the first word
\b   : Word boundary