PHP: is_float - Manual (original) (raw)

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

is_float — Finds whether the type of a variable is float

Description

Note:

To test if a variable is a number or a numeric string (such as form input, which is always a string), you must useis_numeric().

Parameters

value

The variable being evaluated.

Examples

Example #1 is_float() example

`<?php

var_dump

(is_float(27.25));
var_dump(is_float('abc'));
var_dump(is_float(23));
var_dump(is_float(23.5));
var_dump(is_float(1e7)); //Scientific Notation
var_dump(is_float(true));
?>`

The above example will output:

bool(true) bool(false) bool(false) bool(true) bool(true) bool(false)

Found A Problem?

nonzer0value ¶

10 years ago

Coercing the value to float and back to string was a neat trick. You can also just add a literal 0 to whatever you're checking.

<?php
function isfloat($value) {
  // PHP automagically tries to coerce $value to a number
  return is_float($value + 0);
}
?>

Seems to work ok:

<?php
isfloat("5.0" + 0);  // true
isfloat("5.0");  // false
isfloat(5 + 0);  // false
isfloat(5.0 + 0);  // false
isfloat('a' + 0);  // false
?>

YMMV

Boylett ¶

17 years ago

If you want to test whether a string is containing a float, rather than if a variable is a float, you can use this simple little function:

function isfloat($f) return ($f == (string)(float)$f);

Anonymous ¶

4 years ago

is_float() returns true for NAN, INF and -INF. You may want to test is_float($value) && is_finite($value), or alternatively filter_var($value, FILTER_VALIDATE_FLOAT) !== false.

kshegunov at gmail dot com ¶

17 years ago

As celelibi at gmail dot com stated, is_float checks ONLY the type of the variable not the data it holds!

If you want to check if string represent a floating point value use the following regular expression and not is_float(),
or poorly written custom functions.

/^[+-]?(([0-9]+)|([0-9]*\.[0-9]+|[0-9]+\.[0-9]*)|
(([0-9]+|([0-9]*\.[0-9]+|[0-9]+\.[0-9]*))[eE][+-]?[0-9]+))$/

Erutan409 at Hotmail dot com ¶

10 years ago

Boylett's solution is elegant (http://php.net/manual/en/function.is-float.php#85848), but won't work for long float's or variables that are not explicitly type of 'string' or for long floats that are encased in quotes, making it a string that will be truncated/rounded when cast to a float.  So, further logic must be completed to test for the case.  Take the following example:

<?php

if (!function_exists("test_float")) {

    function test_float($test) {

        if (!is_scalar($test)) {return false;}

        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>y</mi><mi>p</mi><mi>e</mi><mo>=</mo><mi>g</mi><mi>e</mi><mi>t</mi><mi>t</mi><mi>y</mi><mi>p</mi><mi>e</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">type = gettype(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8095em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mord mathnormal">p</span><span class="mord mathnormal">e</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord mathnormal">e</span><span class="mord mathnormal">tt</span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mord mathnormal">p</span><span class="mord mathnormal">e</span><span class="mopen">(</span></span></span></span>test);

        if ($type === "float") {
            return true;
        } else {
            return preg_match("/^\\d+\\.\\d+$/", $test) === 1;
        }

    }

}

$test = "3.14159265358979323846264338g32795";

var_dump($test);
var_dump((float)$test);
var_dump($test == (string)(float)$test);
var_dump(test_float($test));

?>

Will produce (32-bit):

string(34) "3.14159265358979323846264338g32795"
float(3.1415926535898)
bool(false)
bool(false)

So far, so good, right?  Yeah, but it's misleading, because the string is so long, that when it's converted to a float, it won't be equivalent to the comparison of the value being cast back into a string .  So the aforementioned short function works.  Look at this next example:

<?php

$test = 3.1415926535897932384626433832795;

var_dump($test);
var_dump((float)$test);
var_dump($test == (string)(float)$test);
var_dump(test_float($test));

?>

Will produce (32-bit):

float(3.1415926535898)
float(3.1415926535898)
bool(false)
bool(true)

Why is it not working now, but the value is truly a float?  Same reasoning as mentioned before.  The float is so long that it's truncated/rounded and doesn't match the comparison being done with the short-hand function.

So, as you can see, more logic should be applied to the variable you're testing.

KIVagant at gmail dot com ¶

13 years ago

Yet another regular expression for float in real life:

<?php
function isTrueFloat($val)
{
    <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi><mi>a</mi><mi>t</mi><mi>t</mi><mi>e</mi><mi>r</mi><mi>n</mi><msup><mo>=</mo><mo mathvariant="normal" lspace="0em" rspace="0em">′</mo></msup><msup><mi mathvariant="normal">/</mi><mo stretchy="false">[</mo></msup><mo>−</mo><mo>+</mo><mo stretchy="false">]</mo><mo stretchy="false">?</mo><mo stretchy="false">(</mo><mo stretchy="false">(</mo><mo stretchy="false">(</mo><mspace linebreak="newline"></mspace><mspace linebreak="newline"></mspace><mi>d</mi><mo>+</mo><mo stretchy="false">)</mo><mspace linebreak="newline"></mspace><mspace linebreak="newline"></mspace><mi mathvariant="normal">.</mi><mo stretchy="false">?</mo><mo stretchy="false">(</mo><mspace linebreak="newline"></mspace><mspace linebreak="newline"></mspace><mi>d</mi><mo>+</mo><mo stretchy="false">)</mo><mo stretchy="false">?</mo><mo stretchy="false">)</mo><mi mathvariant="normal">∣</mi><mspace linebreak="newline"></mspace><mspace linebreak="newline"></mspace><mi mathvariant="normal">.</mi><mspace linebreak="newline"></mspace><mspace linebreak="newline"></mspace><mi>d</mi><mo>+</mo><mo stretchy="false">)</mo><mo stretchy="false">(</mo><mo stretchy="false">[</mo><mi>e</mi><mi>E</mi><mo stretchy="false">]</mo><mo stretchy="false">?</mo><mo stretchy="false">[</mo><mo>+</mo><mo>−</mo><mo stretchy="false">]</mo><mo stretchy="false">?</mo><mspace linebreak="newline"></mspace><mspace linebreak="newline"></mspace><mi>d</mi><mo>+</mo><mo stretchy="false">)</mo><mo stretchy="false">?</mo></mrow><annotation encoding="application/x-tex">pattern = &#x27;/^[-+]?(((\\\\d+)\\\\.?(\\\\d+)?)|\\\\.\\\\d+)([eE]?[+-]?\\\\d+)?</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.9463em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">p</span><span class="mord mathnormal">a</span><span class="mord mathnormal">tt</span><span class="mord mathnormal" style="margin-right:0.02778em;">er</span><span class="mord mathnormal">n</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel"><span class="mrel">=</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.7519em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">′</span></span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1.138em;vertical-align:-0.25em;"></span><span class="mord"><span class="mord">/</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.888em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mopen mtight">[</span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">−</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord">+</span><span class="mclose">]?</span><span class="mopen">(((</span></span><span class="mspace newline"></span><span class="mspace newline"></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">d</span><span class="mord">+</span><span class="mclose">)</span></span><span class="mspace newline"></span><span class="mspace newline"></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord">.</span><span class="mclose">?</span><span class="mopen">(</span></span><span class="mspace newline"></span><span class="mspace newline"></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">d</span><span class="mord">+</span><span class="mclose">)?)</span><span class="mord">∣</span></span><span class="mspace newline"></span><span class="mspace newline"></span><span class="base"><span class="strut" style="height:0.1056em;"></span><span class="mord">.</span></span><span class="mspace newline"></span><span class="mspace newline"></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">d</span><span class="mord">+</span><span class="mclose">)</span><span class="mopen">([</span><span class="mord mathnormal">e</span><span class="mord mathnormal" style="margin-right:0.05764em;">E</span><span class="mclose">]?</span><span class="mopen">[</span><span class="mord">+</span><span class="mord">−</span><span class="mclose">]?</span></span><span class="mspace newline"></span><span class="mspace newline"></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">d</span><span class="mord">+</span><span class="mclose">)?</span></span></span></span>/';

    return (!is_bool($val) && (is_float($val) || preg_match($pattern, trim($val))));
}
?>

// Matches:
1, -1, 1.0, -1.0, '1', '-1', '1.0', '-1.0', '2.1', '0', 0, ' 0 ', ' 0.1 ', ' -0.0 ', -0.0, 3., '-3.', '.27', .27, '-0', '+4', '1e2', '+1353.0316547', '13213.032468e-13465', '-8E+3', '-1354.98879e+37436'

// Non-matches:
false, true, '', '-', '.a', '-1.a', '.a', '.', '-.', '1+', '1.3+', 'a1', 'e.e', '-e-4', 'e2', '8e', '3,25'

PHP: is_float - Manual (original) (raw)

Description

Parameters

Examples

See Also

Found A Problem?