PHP 8.3.4 Released!

is_numeric

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

is_numeric Verifica se una variabile è un numero o una stringa numerica

Descrizione

is_numeric(mixed $var): bool

Verifica se una variabile è un numero. Le stringhe numeriche consistono in segni opzionali, qualsiasi numero di cifre, parte decimale opzionale e parte esponenziale opzionale. Quindi +0123.45e6 è un valore numerico valido. Le notazioni Esadecimali (per esempio 0xf4c3b00c), Binarie (per esempio 0b10100111001), Ottali (per esempio 0777) non sono consentite.

Elenco dei parametri

var

La variabile da valutare.

Valori restituiti

Restituisce true se var è un numero o una stringa numerica, false in caso contrario.

Esempi

Example #1 Esempi di is_numeric()

<?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;
}
}
?>

Il precedente esempio visualizzerà:

'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

Log delle modifiche

Versione Descrizione
7.0.0 Le stringhe nella notazione esadecimale (per esempio 0xf4c3b00c) non sono più considerate come stringhe numeriche, ovvero is_numeric() ora restituisce false.

Vedere anche:

  • ctype_digit() - Controlla i caratteri numerici
  • is_bool() - Verifica se una variabile è di tipo boolean
  • is_null() - Verifica se la variabile è di tipo null
  • is_float() - Verifica se una variabile è di tipo float (decimale a virgola mobile)
  • is_int() - Verifica se una variabile è di tipo integer
  • is_string() - Verifica se il tipo di una variabile sia stringa
  • is_object() - Verifica se una variabile è un object
  • is_array() - Verifica se una variabile è un array

add a note

User Contributed Notes 8 notes

up
93
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.
up
32
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
up
12
moskalyuk at gmail dot com
17 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
9
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...
up
3
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.
up
3
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);
}
up
2
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
up
-6
anantkumarsingh03101988 at gmail dot com
1 year ago
Example #2

Output:

'9001 ' is NOT numeric

is incorrect for PHP8, it's numeric.

So please correct this.
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