- strpos: documentation ( source)
- preg_match: documentation ( source)
<?php
$str[] = "01C8000100023543900000133243";
$str[] = "01C80010023543xxxxx3243";
$str[] = "1543344=-23-1--923243";
$pattern = "/3543(.+)3243/";
foreach($str as $key=>$string) {
if(preg_match($pattern,$string,$res)) {
echo "found in $string: ".$res[1]." starts at position ".strpos($string,$res[1])."\r\n";
}
else {
echo "not found in $string"."\r\n";
}
}