is_numeric

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

is_numeric — Finds whether a variable is a number or a numeric string

Опис

is_numeric(mixed $value): bool

Determines if the given variable is a number or a numeric string.

Параметри

value: The variable being evaluated.

Значення, що повертаються

Returns true if value is a number or a numeric string, false otherwise.

Журнал змін

Версія	Опис
8.0.0	Numeric strings ending with whitespace (`"42 "`) will now return `true`. Previously, `false` was returned instead.

Приклади

Приклад #1 is_numeric() examples

<?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($element, true) . " is numeric", PHP_EOL;
    } else {
        echo var_export($element, true) . " is NOT numeric", PHP_EOL;
    }
}
?>

Поданий вище приклад виведе:

'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

Приклад #2 is_numeric() with whitespace

<?php
$tests = [
    " 42",
    "42 ",
    "\u{A0}9001", // non-breaking space
    "9001\u{A0}", // non-breaking space
];

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

В PHP 8 поданий вище приклад виведе:

' 42' is numeric
'42 ' is numeric
' 9001' is NOT numeric
'9001 ' is NOT numeric

В PHP 7 поданий вище приклад виведе:

' 42' is numeric
'42 ' is NOT numeric
' 9001' is NOT numeric
'9001 ' is NOT numeric

Прогляньте також

Numeric strings
ctype_digit() - Check for numeric character(s)
is_bool() - Finds out whether a variable is a boolean
is_null() - Перевіряє чи змінна має значення 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() - Перевіряє, чи має задана змінна рядковий тип даних
is_object() - Finds whether a variable is an object
is_array() - Finds whether a variable is an array
filter_var() - Filters a variable with a specified filter

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User Contributed Notes 7 notes

down

sobolanx at gmail dot com ¶

13 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.

down

tanguy_barsik at hotmail dot com ¶

7 years ago

for strings, it return true only if float number has a dot

is_numeric( '42.1' )//true
is_numeric( '42,1' )//false

down

moskalyuk at gmail dot com ¶

18 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

down

ben at chico dot com ¶

10 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...

down

kouber at saparev dot com ¶

20 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);
}

down

Magnus Deininger, dma05 at web dot de ¶

15 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.

down

Katrina Kizenbach ¶

1 year ago

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

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