is_numeric

(PHP 4, PHP 5, PHP 7, PHP 8)

is_numeric 检测变量是否为数字或数字字符串

说明

is_numeric(mixed $value): bool

检测指定的变量是否为数字或数字字符串

参数

value

需要检测的变量。

返回值

如果 value 是数字或数字字符串, 返回 true;否则返回 false

范例

示例 #1 is_numeric() 示例

<?php
$tests 
= array(
    
"42",
    
1337,
    
0x539,
    
02471,
    
0b10100111001,
    
1337e0,
    
"0x539",
    
"02471",
    
"0b10100111001",
    
"1337e0",
    
"not numeric",
    array(),
    
9.1,
    
null,
    
'',
);

foreach (
$tests as $element) {
    if (
is_numeric($element)) {
        echo 
var_export($elementtrue) . " is numeric"PHP_EOL;
    } else {
        echo 
var_export($elementtrue) . " is NOT numeric"PHP_EOL;
    }
}
?>

以上例程会输出:

'42' is numeric
1337 is numeric
1337 is numeric
1337 is numeric
1337 is numeric
1337.0 is numeric
'0x539' is NOT numeric
'02471' is numeric
'0b10100111001' is NOT numeric
'1337e0' is numeric
'not numeric' is NOT numeric
array (
) is NOT numeric
9.1 is numeric
NULL is NOT numeric
'' is NOT numeric

参见

add a note add a note

User Contributed Notes 6 notes

up
81
sobolanx at gmail dot com
11 years ago
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.
up
27
tanguy_barsik at hotmail dot com
5 years ago
for strings, it return true only if float number has a dot

is_numeric( '42.1' )//true
is_numeric( '42,1' )//false
up
10
moskalyuk at gmail dot com
15 years ago
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 number
up
5
ben at chico dot com
8 years ago
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...
up
3
kouber at saparev dot com
18 years ago
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.

http://www.php.net/manual/en/language.types.float.php

In such a case, it is suitable to use regular expressions:

function is_numeric_big($s=0) {
  return preg_match('/^-?\d+$/', $s);
}
up
0
Magnus Deininger, dma05 at web dot de
13 years ago
regarding 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.
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