Why is the caret (^) used before the 0 in the regular expression "/[^0-9]/" for character substitution in PHP?

The caret (^) symbol in a regular expression is used to indicate negation. In the regular expression "/[^0-9]/", the caret before the 0 means that we are looking for any character that is not a digit (0-9). This is useful for character substitution in PHP when we want to replace any non-digit characters with a different value. 

$string = "abc123def456ghi";
$replacedString = preg_replace("/[^0-9]/", "*", $string);
echo $replacedString; // Output: ***123***456***

Keywords

caret regular expression character substitution PHP 0

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