PHP (Preg_match)

Question

I’d like you to help define mine preg_match.

This will be for the creation of a textarea form $_POST['text'].

I want the pregmatch to just accept: Strokes, Dots, Bars, + and -, commas, spaces, numbers, letters, #and *.

preg_replace("", $data);

Answer 1

If I understand you want the preg_match valide if it contains only the following types of characters:

• traces
• dots
• bars
• sign of +
• sign of -
• commas
• spaces
• numbers
• letters
• # (hash)
• * (asterisk)

You can use the following regex:

^[a-z0-9\-+, .\#*\\/]+$

In the preg_match would be:

if (empty($_POST['text'])) {
    echo 'Não digitou nada';
} else {
    $text = $_POST['text'];

    if (preg_match('#^[a-z0-9\-+, .\#*\\/]+$#i', $text)) {
        echo 'Validou';
    } else {
        echo 'Não validou';
    }
}

---

Explaining the regex

This regex is very simple:

• o the keys [...] and everything inside them will be accepted (will do the "match")
• the sign of ^ indicates that you should start with exactly the following expression
• the sign of $ indicates that it should end exactly with the previous expression
• The sign of + between the ] and the $ (...]+$) indicates that it must have the format of what is inside [...] until it finds the next expression, as it has no expression, only the $ then ends there, (regardless of the amount of characters)

Extra explanations:

• the a-z indicates that it may contain from A to Z
• the \d indicates that it can contain from 0 to 9 (is equivalent to typing 0-9)
• The \- indicates that it may contain hyphens (dash -), the bar is to escape and not mix with some expression shortcut
• \\ is to accept inverted bars, use two bars so that the regex does not think you are trying to escape the next expression
• The i in #...#i is to consider both uppercase and minuscule letters

^[a-z\d\-+, .\#*\\/]+$
^  ^                ^^
.  .                ..
.  .                .... Termina exatamente com a expressão anterior
.  .                .
.  .                .... busca até o "final" ou até a próxima expressão
.  .
.  ..................... tudo que estiver dentro de `[...]` será valido
.
........................ deve começar exatamente com a próxima expressão