7.7.4 Advanced variable validation using CTYPEThis is NOT the latest copy of this book; click here for the latest version.
For more specific parsing of character types in a variable, the CTYPE library is available. If you want to check for particular values inside a variable, and want to do so very fast, CTYPE is for you. Compared to a test like is_numeric(), the equivalent CTYPE check is about three times faster. There are eleven CTYPE functions in total, all of which work in the same way as is_numeric(): you pass a variable in, and get either true or false back.
The eleven prototypes are:
bool ctype_alnum ( string text)
bool ctype_alpha ( string text)
bool ctype_cntrl ( string text)
bool ctype_digit ( string text)
bool ctype_graph ( string text)
bool ctype_lower ( string text)
bool ctype_print ( string text)
bool ctype_punct ( string text)
bool ctype_space ( string text)
bool ctype_upper ( string text)
bool ctype_xdigit ( string text)
Each of these match different text types, and this table briefly categorises what each function matches:
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ctype_alnum()
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matches A-Z, a-z, 0-9
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ctype_alpha()
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matches A-Z, a-z
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ctype_cntrl()
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matches ASCII control characters
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ctype_digit()
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matches 0-9
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ctype_graph()
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matches values that can be represented graphically
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ctype_lower()
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matches a-z
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ctype_print()
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matches visible characters (not whitespace)
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ctype_punct()
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matches all non-alphanumeric characters (not whitespace)
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ctype_space()
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matches whitespace (space, tab, new line, etc)
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ctype_upper()
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matches A-Z
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ctype_xdigit()
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matches digits in hexadecimal format
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The matches are absolute, which means that ctype_digit() will return false for the value "123456789a" because of the "a" at the end, as this script shows:
<?php
$var = "123456789a";
print (int)ctype_digit($var);
?>
Also note that there is no match for floating-point numbers available, as ctype_digit() matches 0-9 without also matching the decimal point. As a result, it will return false for 123.456. For this purpose you need to use is_float().
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