is_numeric
(PHP 4, PHP 5)
is_numeric — Finds whether a variable is a number or a numeric string
Description
Finds whether the given variable is numeric. Numeric strings consist of optional sign, any number of digits, optional decimal part and optional exponential part. Thus +0123.45e6 is a valid numeric value. Hexadecimal (e.g. 0xf4c3b00c), Binary (e.g. 0b10100111001), Octal (e.g. 0777) notation is allowed too but only without sign, decimal and exponential part.
Parameters
-
var -
The variable being evaluated.
Return Values
Returns TRUE if var is a number or a numeric
string, FALSE otherwise.
Examples
Example #1 is_numeric() examples
<?php
$tests = array(
"42",
1337,
0x539,
02471,
0b10100111001,
1337e0,
"not numeric",
array(),
9.1
);
foreach ($tests as $element) {
if (is_numeric($element)) {
echo "'{$element}' is numeric", PHP_EOL;
} else {
echo "'{$element}' is NOT numeric", PHP_EOL;
}
}
?>
The above example will output:
'42' is numeric '1337' is numeric '1337' is numeric '1337' is numeric '1337' is numeric '1337' is numeric 'not numeric' is NOT numeric 'Array' is NOT numeric '9.1' is numeric
See Also
- ctype_digit() - Check for numeric character(s)
- is_bool() - Finds out whether a variable is a boolean
- is_null() - Finds whether a variable is NULL
- is_float() - Finds whether the type of a variable is float
- is_int() - Find whether the type of a variable is integer
- is_string() - Find whether the type of a variable is string
- is_object() - Finds whether a variable is an object
- is_array() - Finds whether a variable is an array
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Коментарии
Note that this function is not appropriate to check if "is_numeric" for very long strings. In fact, everything passed to this function is converted to long and then to a double. Anything greater than approximately 1.8e308 is too large for a double, so it becomes infinity, i.e. FALSE. What that means is that, for each string with more than 308 characters, is_numeric() will return FALSE, even if all chars are digits.
However, this behaviour is platform-specific.
language.types.float
In such a case, it is suitable to use regular expressions:
function is_numeric_big($s=0) {
return preg_match('/^-?\d+$/', $s);
}
is_numeric fails on the hex values greater than LONG_MAX, so having a large hex value parsed through is_numeric would result in FALSE being returned even though the value is a valid hex numberregarding the global vs. american numeral notations, it should be noted that at least in japanese, numbers aren't grouped with an extra symbol every three digits, but rather every four digits (for example 1,0000 instead of 10.000). also nadim's regexen are slightly suboptimal at one point having an unescaped '.' operator, and the whole thing could easily be combined into a single regex (speed and all).
adjustments:
<?php
$eng_or_world = preg_match
('/^[+-]?'. // start marker and sign prefix
'(((([0-9]+)|([0-9]{1,4}(,[0-9]{3,4})+)))?(\\.[0-9])?([0-9]*)|'. // american
'((([0-9]+)|([0-9]{1,4}(\\.[0-9]{3,4})+)))?(,[0-9])?([0-9]*))'. // world
'(e[0-9]+)?'. // exponent
'$/', // end marker
$str) == 1;
?>
i'm sure this still isn't optimal, but it should also cover japanese-style numerals and it fixed a couple of other issues with the other regexen. it also allows for an exponent suffix, the pre-decimal digits are optional and it enforces using either grouped or ungrouped integer parts. should be easier to trim to your liking too.
Note that the function accepts extremely big numbers and correctly evaluates them.
For example:
<?php
$v = is_numeric ('58635272821786587286382824657568871098287278276543219876543') ? true : false;
var_dump ($v);
?>
The above script will output:
bool(true)
So this function is not intimidated by super-big numbers. I hope this helps someone.
PS: Also note that if you write is_numeric (45thg), this will generate a parse error (since the parameter is not enclosed between apostrophes or double quotes). Keep this in mind when you use this function.
Apparently NAN (Not A Number) is a number for the sake of is_numeric().
<?php
echo "is ";
if (!is_numeric(NAN))
echo "not ";
echo "a number";
?>
Outputs "is a number". So something that is NOT a number (by defintion) is a number...
for strings, it return true only if float number has a dot
is_numeric( '42.1' )//true
is_numeric( '42,1' )//false
Note that is_numeric() will evaluate to false for number strings using decimal commas.
is_numeric('0.11');
Output: true
is_numeric('0,11');
Output: false