检查子字符串是否包含在实际字符串的任何位置

Question

I have the following string:

$str = "A string".

When I use:

preg_match("/A string/", $str)

I get the match everything works perfectly fine, but I want to use the same regular expression for another string:

$str2 = "A test string".

For this case I can use:

"/A (test  )?string/"

But I want it to be more complex, it should also be able to match strings like this, for example:

A st ring
 A string

I mean that the substring "test " can appear anywhere in the subject.

Is it even possible to find a regular expression for this?

Answer 1

You could try something like this

$str = "My test String";
    if (strpos($str, 'test') !== false) {
        echo 'true';
    }

Answer 2

Try this:

$str = "A sttest ring";
$newstr = preg_replace("/\s*test\s*/", "", $str);
preg_match("/A string/", $newstr, $matches);
echo $matches ? 'true' : 'false';

Online Demo

Answer 3

I would create a function for that:

function containsLetters($testString, $lettersString, $caseSensitive = false, $whiteSpaces = false){
  if(!$caseSensitive){
    $testString = strtolower($testString); $lettersString = strtolower($lettersString);
  }
  if($whiteSpaces){
    $tw = $testString; $lw = $lettersString;
  }
  else{
    $tw = preg_replace('/\s/', '', $testString); $lw = preg_replace('/\s/', '', $lettersString);
  }
  $tst  = str_split($tw); $ltr = str_split($lw); $c = count($ltr); $r = array();
  foreach($ltr as $l){
    foreach($tst as $i => $t){
      if($l === $t){
        $a = array_splice($tst, $i, 1); $r[] = $a[0];
      }
    }
  }
  if(count($r) >= $c){
    return true;
  }
  return false;
}
$test = containsLetters('A sttest ring', 'a test string');

Just pass true to the 3rd argument to make it case sensitive. Also, pass true to the 4th argument to compare white spaces.