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How we list which characters we DON'T want ?How to use backslash character

Andrew Deniel 2904 08-Jun-2013
asp.net asp.net 
Updated on 15-Sep-2020
Andrew Deniel

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Andrew Deniel

Andrew Deniel

08-Jun-2013
We can list which characters we DON'T want so just use a '^' as the first symbol in a bracket expression
(i.e., "%[^a-zA-Z]%" matches a string with a character that is not a letter between two percent signs).
"^[a-zA-Z]": a string that starts with a letter;
"[0-9]%": a string that has a single digit before a percent sign;
",[a-zA-Z0-9]$": a string that ends in a comma followed by an alphanumeric character. 

In order to be taken literally, you must escape the characters "^.[$()|*+?{\" with a backslash ('\'), as they have special meaning. On top of that, you must escape the backslash character itself in PHP3 strings, so, for instance, the regular expression "(\$|¥)[0-9]+" would have the function call: ereg("(\\$|¥)[0-9]+", $str)
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