$re = '/\+?|0*|(972)?(.*)/';
$str = '0527691234
00527691234
527691234
00972527691234
972527691234
+972527691234
';
$subst = "$2";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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