Regular Expression

Many scripts tend to reply on regular expression to validate the input specified by user. While validating input is a superb idea, doing so via regular expression can be quite slow. In many cases the process of validation merely involved checking the source string against a certain character list such as A-Z or 0-9, etc... Instead of using regex in many instances you can instead use the ctype extension (enabled by default since PHP 4.2.0) to do the same. The ctype extension offers a series of function wrappers around C's is*() function that check whether a particular character is within a certain range. Unlike the C function that can only work a character at a time, PHP function can operate on entire strings and are far faster then equivalent regular expressions.
Ex.
preg_match("![0-9]+!", $foo);
vs
ctype_digit($foo);

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