PHP program related to stringpos() function issue

Question

$text = $_POST['text'];  
$find = $_POST['find'];
$offset = 0;
while ($offset < strlen($text))
{
   $pos = strpos($text, $find, $offset);
   $offset += strlen($find);
   echo "$find found in $pos <br>";
}

There is something wrong with this program. All I want to do is print all the positions in which $find is located in $text.

Tell me what the problem is. Try not to change the while condition. Thanks in advance.

Answer 1

First of all you need to break out of your loop if its not found. And secondly, what I think you want to do is to jump to the point in the $text just after where you found the last $find:

$text = $_POST['text'];  
$find = $_POST['find'];
$offset = 0;
while ($offset < strlen($text))
{
   $pos = strpos($text, $find, $offset);
   // $offset += strlen($find); // removed
   if ( $pos===false ) break;
   $offset = $pos+1;
   echo "$find found in $pos <br>";
}

Answer 2

Another, more compact way to do this would be something like this:

while ( ($pos=strpos($text,$find,$offset)) !== false) {
    echo "$find found in $pos <br>";
    $offset = $pos+1;
}

Answer 3

Why not use a regex like this:

$text = 'hello world, I want to find you world';
$find = 'world';

preg_match_all('/'.preg_quote($find, '/').'/', $text, $matches, PREG_OFFSET_CAPTURE);
echo '<pre>';
print_r($matches);
echo '</pre>';

Return:

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [0] => world
                    [1] => 6
                )

            [1] => Array
                (
                    [0] => world
                    [1] => 32
                )

        )

)

To get the same output use this:

$text = $_POST['text'];  
$find = $_POST['find'];
preg_match_all('/'.preg_quote($find, '/').'/', $text, $matches, PREG_OFFSET_CAPTURE);
foreach ($matches[0] as $match) {
    echo "$find found in {$match[1]}<br>";
}