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6_functions
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isnumber
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2001-03-21
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Synopsis:
$isalpha(<text>)
$isdigit(<text>)
$isnumber(<text> <base>>)
Technical:
These function test whether the first character in the given string is
an alphabetical character or a digit. Only the first character is
tested.
The function $isnumber() is very similar to $isdigit(), except that
it takes two arguments, the second specifying the numeric base of <text>.
The second argument must be prefixed with a 'b'; eg. "b8" for base 8, "b16"
for base 16. And as always, numbers in base 16 may be prefixed with "0x".
Practical:
These functions are useful for testing an input string to see whether it
is a number or a text string. One use for this might be to check if it
would be suitable input for $iptoname() or $nametoip(). Keep in mind
that only the first character is tested, so this isn't a reliable way
to see if the entire string is a number.
Returns:
"true" or "false" value if first character is a letter or a digit
Examples:
$isalpha(hello) returns true
$isalpha(2hello) returns false
$isdigit(123) returns true
$isdigit(2abc) returns true
$isdigit(a123) returns false
$isnumber(0x9FF b16) returns true