[php] How do I convert a string to a number in PHP?

I want to convert these types of values, '3', '2.34', '0.234343', etc. to a number. In JavaScript we can use Number(), but is there any similar method available in PHP?

Input             Output
'2'               2
'2.34'            2.34
'0.3454545'       0.3454545

If you want the numerical value of a string and you don't want to convert it to float/int because you're not sure, this trick will convert it to the proper type:

function get_numeric($val) {
  if (is_numeric($val)) {
    return $val + 0;
  }
  return 0;
}

Example:
<?php
get_numeric('3'); // int(3)
get_numeric('1.2'); // float(1.2)
get_numeric('3.0'); // float(3)
?>

Source: https://www.php.net/manual/en/function.is-numeric.php#107326

Here is a function I wrote to simplify things for myself:

It also returns shorthand versions of boolean, integer, double and real.

function type($mixed, $parseNumeric = false)
{        
    if ($parseNumeric && is_numeric($mixed)) {
        //Set type to relevant numeric format
        $mixed += 0;
    }
    $t = gettype($mixed);
    switch($t) {
        case 'boolean': return 'bool'; //shorthand
        case 'integer': return 'int';  //shorthand
        case 'double': case 'real': return 'float'; //equivalent for all intents and purposes
        default: return $t;
    }
}

Calling type with parseNumeric set to true will convert numeric strings before checking type.

Thus:

type("5", true) will return int

type("3.7", true) will return float

type("500") will return string

Just be careful since this is a kind of false checking method and your actual variable will still be a string. You will need to convert the actual variable to the correct type if needed. I just needed it to check if the database should load an item id or alias, thus not having any unexpected effects since it will be parsed as string at run time anyway.

Edit

If you would like to detect if objects are functions add this case to the switch:

case 'object': return is_callable($mixed)?'function':'object';

In addition to Boykodev's answer I suggest this:

Input             Output
'2' * 1           2 (int)
'2.34' * 1        2.34 (float)
'0.3454545' * 1   0.3454545 (float)

If you want get a float for $value = '0.4', but int for $value = '4', you can write:

$number = ($value == (int) $value) ? (int) $value : (float) $value;

It is little bit dirty, but it works.

Different approach:

1. Push it all into an array / associative array.
2. json_encode($your_array, JSON_NUMERIC_CHECK); optionally decode it back
3. ?
4. Profit!

Here is the function that achieves what you are looking for. First we check if the value can be understood as a number, if so we turn it into an int and a float. If the int and float are the same (e.g., 5 == 5.0) then we return the int value. If the int and float are not the same (e.g., 5 != 5.3) then we assume you need the precision of the float and return that value. If the value isn't numeric we throw a warning and return null.

function toNumber($val) {
    if (is_numeric($val)) {
        $int = (int)$val;
        $float = (float)$val;

        $val = ($int == $float) ? $int : $float;
        return $val;
    } else {
        trigger_error("Cannot cast $val to a number", E_USER_WARNING);
        return null;
    }
}

You can use:

((int) $var)   ( but in big number it return 2147483647 :-) )

But the best solution is to use:

if (is_numeric($var))
    $var = (isset($var)) ? $var : 0;
else
    $var = 0;

Or

if (is_numeric($var))
    $var = (trim($var) == '') ? 0 : $var;
else
    $var = 0;

Just a little note to the answers that can be useful and safer in some cases. You may want to check if the string actually contains a valid numeric value first and only then convert it to a numeric type (for example if you have to manipulate data coming from a db that converts ints to strings). You can use is_numeric() and then floatval():

$a = "whatever"; // any variable

if (is_numeric($a)) 
    var_dump(floatval($a)); // type is float
else 
    var_dump($a); // any type

//Get Only number from string
$string = "123 Hello Zahid";
$res = preg_replace("/[^0-9]/", "", $string);
echo $res."<br>";
//Result 123

You can always add zero to it!

Input             Output
'2' + 0           2 (int)
'2.34' + 0        2.34 (float)
'0.3454545' + 0   0.3454545 (float)

In whatever (loosely-typed) language you can always cast a string to a number by adding a zero to it.

However, there is very little sense in this as PHP will do it automatically at the time of using this variable, and it will be cast to a string anyway at the time of output.

Note that you may wish to keep dotted numbers as strings, because after casting to float it may be changed unpredictably, due to float numbers' nature.

I've found that in JavaScript a simple way to convert a string to a number is to multiply it by 1. It resolves the concatenation problem, because the "+" symbol has multiple uses in JavaScript, while the "*" symbol is purely for mathematical multiplication.

Based on what I've seen here regarding PHP automatically being willing to interpret a digit-containing string as a number (and the comments about adding, since in PHP the "+" is purely for mathematical addition), this multiply trick works just fine for PHP, also.

I have tested it, and it does work... Although depending on how you acquired the string, you might want to apply the trim() function to it, before multiplying by 1.

There are a few ways to do so:

1. Cast the strings to numeric primitive data types:

   $num = (int) "10";
   $num = (double) "10.12"; // same as (float) "10.12";
   

2. Perform math operations on the strings:

   $num = "10" + 1;
   $num = floor("10.1");
   

3. Use intval() or floatval():

   $num = intval("10");
   $num = floatval("10.1");
   

4. Use settype().

To avoid problems try intval($var). Some examples:

<?php
echo intval(42);                      // 42
echo intval(4.2);                     // 4
echo intval('42');                    // 42
echo intval('+42');                   // 42
echo intval('-42');                   // -42
echo intval(042);                     // 34 (octal as starts with zero)
echo intval('042');                   // 42
echo intval(1e10);                    // 1410065408
echo intval('1e10');                  // 1
echo intval(0x1A);                    // 26 (hex as starts with 0x)
echo intval(42000000);                // 42000000
echo intval(420000000000000000000);   // 0
echo intval('420000000000000000000'); // 2147483647
echo intval(42, 8);                   // 42
echo intval('42', 8);                 // 34
echo intval(array());                 // 0
echo intval(array('foo', 'bar'));     // 1
?>

All suggestions lose the numeric type.

This seems to me a best practice:

function str2num($s){
// Returns a num or FALSE
    $return_value =  !is_numeric($s) ? false :               (intval($s)==floatval($s)) ? intval($s) :floatval($s);
    print "\nret=$return_value type=".gettype($return_value)."\n";
}

$a = "10";

$b = (int)$a;

You can use this to convert a string to an int in PHP.

Only multiply the number by 1 so that the string is converted to type number.

//String value
$string = "5.1"
if(is_numeric($string)){
  $numeric_string = $string*1;
}

If you don't know in advance if you have a float or an integer,
and if the string may contain special characters (like space, €, etc),
and if it may contain more than 1 dot or comma,
you may use this function:

// This function strip spaces and other characters from a string and return a number.
// It works for integer and float.
// It expect decimal delimiter to be either a '.' or ','
// Note: everything after an eventual 2nd decimal delimiter will be removed.
function stringToNumber($string) {
    // return 0 if the string contains no number at all or is not a string:
    if (!is_string($string) || !preg_match('/\d/', $string)) {
        return 0;
    } 

    // Replace all ',' with '.':
    $workingString = str_replace(',', '.', $string);

    // Keep only number and '.':
    $workingString = preg_replace("/[^0-9.]+/", "", $workingString);

    // Split the integer part and the decimal part,
    // (and eventually a third part if there are more 
    //     than 1 decimal delimiter in the string):
    $explodedString = explode('.', $workingString, 3);

    if ($explodedString[0] === '') {
        // No number was present before the first decimal delimiter, 
        // so we assume it was meant to be a 0:
        $explodedString[0] = '0';
    } 

    if (sizeof($explodedString) === 1) {
        // No decimal delimiter was present in the string,
        // create a string representing an integer:
        $workingString = $explodedString[0];
    } else {
        // A decimal delimiter was present,
        // create a string representing a float:
        $workingString = $explodedString[0] . '.' .  $explodedString[1];
    }

    // Create a number from this now non-ambiguous string:
    $number = $workingString * 1;

    return $number;
}

PHP will do it for you within limits

<?php
   $str = "3.148";
   $num = $str;

   printf("%f\n", $num);
?>

Yes, there is a similar method in PHP, but it is so little known that you will rarely hear about it. It is an arithmetic operator called "identity", as described here:

Aritmetic Operators

To convert a numeric string to a number, do as follows:

$a = +$a;

Instead of having to choose whether to convert the string to int or float, you can simply add a 0 to it, and PHP will automatically convert the result to a numeric type.

// Being sure the string is actually a number
if (is_numeric($string))
    $number = $string + 0;
else // Let the number be 0 if the string is not a number
    $number = 0;

In PHP you can use intval(string) or floatval(string) functions to convert strings to numbers.

I got the question "say you were writing the built in function for casting an integer to a string in PHP, how would you write that function" in a programming interview. Here's a solution.

$nums = ["0","1","2","3","4","5","6","7","8","9"];
$int = 15939; 
$string = ""; 
while ($int) { 
    $string .= $nums[$int % 10]; 
    $int = (int)($int / 10); 
} 
$result = strrev($string);

I've been reading through answers and didn't see anybody mention the biggest caveat in PHP's number conversion.

The most upvoted answer suggests doing the following:

$str = "3.14"
$intstr = (int)$str // now it's a number equal to 3

That's brilliant. PHP does direct casting. But what if we did the following?

$str = "3.14is_trash"
$intstr = (int)$str

Does PHP consider such conversions valid?

Apparently yes.

PHP reads the string until it finds first non-numerical character for the required type. Meaning that for integers, numerical characters are [0-9]. As a result, it reads 3, since it's in [0-9] character range, it continues reading. Reads . and stops there since it's not in [0-9] range.

Same would happen if you were to cast to float or double. PHP would read 3, then ., then 1, then 4, and would stop at i since it's not valid float numeric character.

As a result, "million" >= 1000000 evaluates to false, but "1000000million" >= 1000000 evaluates to true.

See also:

https://www.php.net/manual/en/language.operators.comparison.php how conversions are done while comparing

https://www.php.net/manual/en/language.types.string.php#language.types.string.conversion how strings are converted to respective numbers

You can use:

(int)(your value);

Or you can use:

intval(string)

Simply you can write like this:

<?php
    $data = ["1","2","3","4","5"];
    echo json_encode($data, JSON_NUMERIC_CHECK);
?>

You can change the data type as follows

$number = "1.234";

echo gettype ($number) . "\n"; //Returns string

settype($number , "float");

echo gettype ($number) . "\n"; //Returns float

For historical reasons "double" is returned in case of a float.

PHP Documentation

There is a way:

$value = json_decode(json_encode($value, JSON_NUMERIC_CHECK|JSON_PRESERVE_ZERO_FRACTION|JSON_UNESCAPED_SLASHES), true);

Using is_* won't work, since the variable is a: string.

Using the combination of json_encode() and then json_decode() it's converted to it's "true" form. If it's a true string then it would output wrong.

$num = "Me";
$int = (int)$num;
$float = (float)$num;

var_dump($num, $int, $float);

Will output: string(2) "Me" int(0) float(0)

Late to the party, but here is another approach:

function cast_to_number($input) {
    if(is_float($input) || is_int($input)) {
        return $input;
    }
    if(!is_string($input)) {
        return false;
    }
    if(preg_match('/^-?\d+$/', $input)) {
        return intval($input);
    }
    if(preg_match('/^-?\d+\.\d+$/', $input)) {
        return floatval($input);
    }
    return false;
}

cast_to_number('123.45');       // (float) 123.45
cast_to_number('-123.45');      // (float) -123.45
cast_to_number('123');          // (int) 123
cast_to_number('-123');         // (int) -123
cast_to_number('foo 123 bar');  // false

One of the many ways it can be achieved is this:

$fileDownloadCount          =  (int) column_data_from_db;
$fileDownloadCount++;

The second line increments the value by 1.