$re = '/^(?:[a-z0-9] *){3,}(?:\+ *(?:[a-z0-9] *){3,})*$/m';
$str = 'sss
sdfsgdf
4534534
dfs34543
sdafds+3232+sfdsafd
qwe+sdf
234+567
cvb+243
jc + fjewif + fjeie
jc f+ fjewif + fjeie
a
aa
a+
aa+
+aa
+a
a+a
aa+aa
aaa+a';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($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