$re = '/\{(.|\s)*\}/xm';
$str = 'test string is with lot of text and this part {
"List": [{
"ID": "175114",
"Number": "28992"
}]
} and more text goes here after the valid JSON';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php