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<?php function stringValidator($field) { if(!empty($field) && preg_match('~[^a-z\d]~i', $field)) { return "You typed $field: please don't use special characters '<' '>' '_' '/' etc."; } return "valid"; // empty or valid } $strings = ["hello", "what_the"]; foreach ($strings as $string) { echo "$string: " , stringValidator($string) , "\n"; }
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.27, 8.4.1 - 8.4.14
hello: valid what_the: You typed what_the: please don't use special characters '<' '>' '_' '/' etc.
preferences:
110 ms | 408 KiB | 5 Q