Question

I would like to remove all characters that do not match a specified Regex.

for example

$a = "hello my name is ,pate !";

echo notin_replace("[a-zA-Z]","",$a);

hello my name is pate

Answer 1

[^a-zA-Z]

Mind the carret at the beginning of the character class. It means not.

$a = "hello my name is ,pate !";

echo preg_replace("([^a-zA-Z ])", "", $a);

hello my name is pate

Don’t forget to add space as well to the allowed characters, otherwise it would be removed.